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it Into two portions; treat the flr«t directly with the bichromate, and the second portion must be treated with zinc, and afterwards with bichromate; the first will plv- the amount of iron as protoxide, and this amount If subtracted from the amount of the second, will give the peroxide.

Query 21M —It would be n'most impossible to give a test for alcohol in any kind of liquid; the tests must often be modified to Miii the liquid. If " Alcohol" will give the liquid in which he suspects alcohol, 1 may perhaps help hi in.

"UudlR."query2'5G,may extract the gold from the sand by boiling it with aqua rc^ta mitrohydrochlma acid) Chloride of gold is formed, and may be obtained by dissolving In water and crystallising. if, however, metallic gold I* wanted, It may be precipitated by adding ferrous Hiii ph ate, which thrown down the gold as a black powder, which may be fused with borax Into A button. Geo. E. Davis

The next operation in water analysis is to determine tbe nmount of " skeletons " of sewage, as Frankland cnlls the nitrates and nitrites :— Take one pint (7000 grains), and evaporate to loz., add silver sulphate to precipitate the chlorides, filter and evaporate to a very smnll bulk; this is placed in the cup of the tube C iu the figure, and admitted under the stopcock; concentrated Bulphurlc acid is then admitted, 4ind the mlxturo gently agitated, nitric oxide is expelled, which mny be accurately measured, and the amount of nitrates calculated. Tbe nitrates vary much In quautity, sometimes being absent altogether, and at others existiug in quantities as much as 20 grains per gallon.

"Basin," query 2192.—I suppose the quantity of ammonia contained in the sulphate is what " Basin" requires.

Place 17grms. of the sulphate In a small distilling apparatus, with an excess of potash solution, and apply heat; conduct the ammouiii, which Is liberated, Into 50cbc. of a noruinl solution of sulphuric acid. When all the ammonia has paused over, colour the normal «cid with litmus, and neutralise with normal alkali, notlug the number of cbc. u-ed; the number used subtracted from 50 gives the percentage of ammonia. If the sulphate Is u very impure variety, and it Is required to know how much sulphate it contains, take fi ligrms., and proceed in the same manner only conduct the liberated ammouta into 1< 0 cbc. of normal acid; the number of cbc. of acid actually neutralised 'represents the percentage ol sulphate of ammonia.

To " Dlsclpulus," query 2107 — 1. Dissolve Igrm. of the sample of salt-cake iu 100c be. of water; then dissolve 122 grammes of barium chloride hi a litre of water, and add to5 cbc. of the salt cake solution uutil ft occasion- no further precipitate. A small filtering tube must be frequently useu, as the end uf the precipitation may he overstepped. Each cbc. of solution is equal to 0' • 96 80}, or 004 grm. S< >a. 2. He may separate barium from Btrontium by exactly neutralising the solution, and adding potassium bichromate (Kj Cr* O?); the barium Is precipitated as nn Insoluble chromnie of a yellow colour, whilst the strontium lemaius in the solution. The barium chroma to is decomposed by acids. 3, Dissolve 17 ■ rains nitrate of silver in a litre of water; each cbc. of this solution Indicates 0"003;V)grm. of chlorine To determine the amount of chlorine in any polution, a few drops: of potassium cbromatc are added, aud then the silver nitrate solution, until after well stirring a blood colour 1b still manifest. The number of cbc used x 000.J55 gives the amount of chlorine. 4. Stauden's patent manure, which is a bono phosphate, need only be examined for soluble phosphates and ammonia. Ammonia does not exlnt in the manure, but 1s formed by the decomposition of the gehuiu. Estimate the phosphoric acid thus: —Dissolve fi i> grammes of uranium nitrate (crystallised) in lOOcbc, of water, each cbc = OOOlgrm. of VOi. It the V* Oa is required, W31 grammes must be dissolved In lOOcbc. of water. Briug a known weight of the manure Into solution, filter and add a solution of acet.ite of sodium and acetic acid, then add fie uranium solution until a drop taken out produces 11 brown coloration when placed in contact with fcrrocyauideof potassium. The number of cbc. used, multiplied by Q>001, gives the amount of phosphoric acid. To estimate the ammonia, he muitt add caustic potash, or soda lime in * distilling flask, uud lead the ammonia into normal sulphuric acid ; 17 grammes of ammonia will neutralise lOOcbc of the normal acid.

J. Crompton, query 2271, may purify his ncld by distilling it in aglMB$?etort. Of course he cannot cheaply recover the nitric ncid from the nitrate-*, which result from tbe action of the aeld on the metal.

"Izgltzar," query 2270, li referred to page 003, Vol X., for a method to estimate the amount of organic matter in water.

"J.N. from tbe North Country,*' query 2325, must take lOyrms. of Iron ore, and dissolve it iu hydrochloric, and procecl with the bichromate of pntat-Hiuin solution, as I have Ftated ou page 605. Vol. X,, save that he must, after bringing the ore into solution, divide

LATHKS.

Sib,—I am sorry to have been the menus of promulgating the grievous error that Mr. Bennett, who invented the die-chuck I sent you two weeks ago, had ever worked iu Air. Evans's shop. I have not seen Mr. Evans since, but am satisfied that Mr Baker malt be better informed than I. Though Mr. Evans is not able to claim the distinction ol having been Mr. Bennett's employer, there Is no reason why he should not have some credit given him in a matter of much greater consequence, nnd which he does not *eem likely to get, Jn your number of April 8 you give n picture of .Mr Salt's lathe, which you say was "chiefly made at jfnltaire, but was finished by a London maker%' I happen to know that a great part of the lathe which teat made at Saltaire, and which came to Mr, Evans's, BH, Wardoar-strect, So ho, London, to be "finished," was put on one side, and entirely re-made. There Is no wonder that it cost a lot of money, as everything that could be was made of steel. The whole of the slide-rest, for instance, Is steel, aud the " bright set of engine-cut wheels" would have been steel if they could have been cut at any reasonable price. They were done Iu the machine of which a drawing forms the front page of No. 253. The "screw headstock,''or poppet head, has the ''base slide" arrangement, which, it it h:\-t not been altered since I last saw it, has the desirable faculty of going over on the wrong side—viz., array from the workman, thin turning cones biggest at the little end. I do not think Mr. Evans had anything to do with the overhead motion further than making some alterations to order; and I hope that his mind is Dot oppressed with the recollection of ever having mnde for such a lathe such a chuck as the lace plate with four doirfl sticking out of It, which is shown on the floor in the picture. J. K. 1".

APPAKKXT PARADOXES IN EQUATION'S.

Sir,—The "apparent paradox," given In a query some time ago, and which has elicited several answers, but which appeur not to he satisfactory to the propo.-er is simply one of those difficulties which present themselves to the student when advancing over the first stepping ■tones to a knowledge of the theory of equations, As it is an important subject to the studeut of mathemHtles, aud may hare been a troublesome one to many of your readers, you will perhaps allow mu a littlo space to endeavour to explain it.

If a = ft, and both sid-s be multiplied by a and h"> taken from both sides we have a7 — A1 ■= ab— 4*, and if the proposer chooses to take a b from both. sides, we have a1 ti* i« — b) = a b b1 (a — 4) Divide both Hides of these two equations by a b, and wo have a + b c 4, or a p o, and a + b — 1= 4—1 or a = o, or tn th-> proposer put it- 2 = 1, which reduces to 1 =0. Now, this anomalous result, a = o, Is exactly what every one conversant with the theory of equations would expect, because it is we'l known thiit if any equation, say of throe degrees, as .rJ — 4' x = o, be produced by the multiplication of three factors, as x + 4, x 4, and x. of which one Is the monomial x. then x = o Is »ne of the roots of th-t equation. The equation proposed by "U. B." is simply the equation aa — a 4 — 0 in a disguised form, of which the two roots are a = b as assumed, nnd a = o. But this Is uo answer to the querist. It Is required to be showu bow the value a ~ 0 arises in au equation, which was built up with the value a ~ b assumed.

Now, tinea a - b, then a — b - o, and if both sides be multiplied by a we have a (a b) = o, because o taken any number a times is 0 still Now, if we divide both sides by a — 4, we obtain a = 0, because o divided by auy quautity can never make any more thuuo.

N-.w, this arises from the fact that when we multiply a — 4 by a we treiit a —4 asif it had some toil and definite magnitude. Instead of its true value mid magnitude, viz , o. Whereas, on the other side we treat 0 at its real Value, o. If we assign 11 a b its real value, than we shall have a times 0, or o on the left hand side of the equation, as well us on the right.

If we t-eai o as s»mo number or magnitude on both sides of ihe equatloit, then the paradoxical result vanishes thus : a— 4 a o. multiplying both sides by a. we have n {a — 4i = n x a. Divide the first side by a 4, aud the secoud by its equivalent o, tbeu we

have a - a —I times a = a, when 0 fs treated as

0 If it were a roal number or magnitude. But it would not suit our purpose to follow such a plan, because we should never obtain above one root to an equation, no matter of what degree It might be, whereas It Is well-known that what are called the " paradoxical" results, give us roots that answer the conditions of the questions in which the equations are involved. Thus: A number squared with 12 added. Is equal to seven times the number; what is the number? Here x* — 7 x + 12 s o, divide both sides by x — 4, and we have x — 3 = o. Hence x = 4, and x 3 are the roots of the equation, cither of which numbers will answer the conditions of the question. If the above equation be tested in the way that a1 — a b =

0 was treated, we get the same apparent paradox. Thus, let x = 4, snd x 4 = o. Multiply both side*

by x — 3—ir, In reality by 1, and we have x2 — 7 x + 12 = o, divide this by x 4, and we have x — 3 = o, orx = 3. T. Bmown.

A GOOD CHEMICAL BATTERY.

Sir.—That it may Interest the readers of this paper,

1 give a descriptlou of a chemical battery which fur simplicity, cheapness coustant power, aud durability, is the best I know ot. It requires very little attention, and Is always ready for use.

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In a wide-mouthed glass jar, having a wooden disc made of a cfg.ir box placed over lis mouth, and pendant from the board, are three copper wires coated with gutta-percha, with their ends turned up, supporting a hollow ring or cylinder of amalgamated zinc of \tn. thickness, tbe lower edge resting ou the turned up ends of the pendant coated wires, the guttapercha covering of the wires preventing contact of the zinc and copper. The zinc cylinder is connected to a wire of copper or platina passing up through the board disc, ana through a binding screw.

Suspended from the centre of tbe disc of wood and hanging plumb in the centre of the cylinder of zinc, without touching it, is a piece of platinised silver (sheet) rolled up, which is connected with a binding screw on the top of the wooden disc by a piece of Its owu metnl ; these two connections andbindlug screws constitute the two terminals.

The jar is to be filled to | or | Its weight with a mixture of oil of vitriol of eC° by Baumc, 1 pait, with 18 parts water, to not quite cover the ztno or platinised silver. The pnrts or the zinc aud platiosed silver exposed above the surface of the acidulated water should be coated with well-boiled coal tar to protect it from the gosei freed from tbe reaction and oxidation.

When not iu Mm- the two metals can be lifted out by means of the wooden disc to which they ate attached, and dipped tttto water to wash them.

AVitli this battery as poworful it current can be had as is compatible with durability% although more powerful currents can be obtained with bichromate of pottasa batteries, but they aro of .short duration and varying power.

1 would recommend that the cylinder of platinised silver be corrugated toobtain more surface of exposure to the acid In a small compass.

Appended Is a sectional drawing of the apparatus, with descriptive reference.

A, ainalgxmated zinc cylinder; B, platinised silver cylinder, which -ln.ul.i be corrugated ; C, cupper wires eoated with gutta-percha, for holding zinc cylinder; D, binding screw terminals: E. wooden disc for supIKirting the cylinders; F, glass jar; G, the top line or surface ot acidulated wuter.

American Subscriber.

ORGAN BUILDING.

Sir,—As many of your subscribers seem interested in the MUbject of organ building I take the liberty of sending you AU idea of my owu for making one pedal pipe do duty for two.

Many attempts have been made to accomplish this feat, but all of them have proved more or less useless. The prevailing idea is that of having a valve at one side of the pipe near the top, to bo operated upon by the pedal key; but the great objection to this is, that the same quantity of wind which causes, say, the C pipe to speak, will prove too much for It when called ■1 ">n to sound C sharp, thereby causing it either to overblow, or else give a different or uneven quality of •ouud.

Now my idea Is not only to have the valve rts before stated, but also to have 2 feet nnd 2 pallets to each pipe, is »t is evident that by 30 doing the wind for each note ■Muild be regulated to a nic.ty.

In fixing the pipes, one foot would be plnced over •tie hole, and the other over the one a semitone nlgtaer, the action would then be thus: On pressing down, say, the C pedal key, the air would be admitted

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acquainted with all the topes which may have
interested them. Intercommunication between secre-
taries would also prove useful in matters which could
not be referred to in the pages of the Mechanic. 1
might enlarge on the many advantagi-s to be derived
from ancb associations, but refrain until my fellow
subscribers have had an opportunity of expie'slng
their Tlews. D. William Kemp. Leitb.

THE -ENGLISH" VELOCIPEDE ON A. NEW
PRINCIPLE, AND OUU ENGLISH KOADS.-II.

{Concluded from page 05.)
Sir —Respecting the proper use of the velocipede. I
will just mention the frequently imprudent use of the
same by those who are
strangers to It. A friend
was once using mine for
the first time, and not
being very strong, he al-
most killed bimaelf by
over exertion; let this be a
warning in others. The use
of the velocipede requires
a tralning;by all, especially
those who are not strong.
Let tbe following points be
particularly observed at
first,viz:—Avoid trying to

ENGLISH MECHANIC MUTUAL IMPROVE-
MENT SOCIETIES.

Sin,—Having been a subscriber for several years, In fact, since tbe commencement of our journal, and having been '.he means of introducing it to several friends, 1 may be allowed to express my pleasure at the appearance of the lirst number of Vol. XI. I have been pleased in watching its gradual development, both In Importance and size, and am glad it is now so generally appreciated by tbe lovers of mechanic*, science, and art, both at home and abroad.

In the editorial article, " Ourselves and Our Subscribers," our talented Editor states tbe fact that the "English Mechanic subscribers may be considered a* members of a vast mutual improvement society who consider it a duty or a privilege to instruct each other." This la so in accordance with my views that 1 am prompted to make one or two suggestions which I have withheld until the present, but uow consider it a Suing opportunity to bring under the notice of our subscribers, and to hear their opinions.

1. That in large towxs where there may be from ten to a hundred subscribers, it would be productive of much good if they could be brought together periodically—say monthly, to discuss the many topics which have been under review in tbe Mechanic during the preceding month. Then one of their number to communicate to this journal anything wbicii mi-lit be considered of sufficient importance, for 1 have no doubt the Editor would willingly allocate a small portion of his valuable space to report the transactions of " The .english Mechanic's Science and Art Societies." Speaking for mjself, I have derived so much pleasure aud instructioa from friendly discussions with tbe few subscribers I know, that I conceive, if done on the large scale, it would prove highly beneficial.

2. It would be a means of increasing the circulation of the English Mechanic by friends being introduced to the meetings, who would doubtless become interested sooner or later in the proceedings, and would of course take In our journal.

3. Engineers and others who hare occasion to remove to other towns, either to new situations or in the way of business, would Und a "society of frieudi" who would sympathise with their every thought, aud

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So fast, avoid going a long
iatauce, and up steep
bills; practice only when
the roads are In good order,
aim at learning the action
and at going slowly ; when
tbe muscles are being sen-
sibly developed, rellnqish
the exercise as soon as pos-
sible, so as to avoid being
fatigued. Go on in this
way for a few weeks and
you may'tben increaee.both
your speed and distance.
Goingat it recklessly at first
is the fruitful eause why
some have turned|awayfrom

the velocipede In disgust, _„,

und now hold it in contempt because, they say. it is
harder work than walking; whereas, had they ob-
served the above rules, a»d had some patience, they
would undoubtedly have come to the opposite conclu-
sion. I have considered tbo machine, and also Its
worker. I now come to the subject of roads. These
three parts are included In the velocipede question.

Since the railways were made and our high roads
have been comparatively deserted, tbe question arises
whether they could not be made of greater use than
now? I think so. Let the Legislature bo petitioned,
and an Act of Parliament ohtalm-d to utilise our great
high roads. Let them be asphalted, or made waterproof
on the suface by some cheap and durable material,
in order to avoid mud In wet weather; velocipedes
could then be used whether flue or wet; or this
plan: let them be divided into three parte—one
side or the road lor foot passengers, the middle
for ordinary traffic, and the other side-say about
three yards wide-appropriated exclusively for
the use of the velocipede, let this part be asphalted or
paved with well-dressed and well-Bet thick flagstones.
Such a road as either of the above woulu be the solution
of the velocipede question; just in like manner as the
railroad was the solution of the use of the steam
engine as a locomotive. But, It may be said, incur-
ring such a largo expense In lonning the roads as
above suggested would never pay. In answer, I would
say, let the velocipedes be taxed. I think no one who
has a velocipede will object to be taxed, provided he
co;ild g t a perfect road to run upon at all times.

In tbe meantime, while the above suggestion Is being ventilated, let us consider if the present system of mending our roads can bo Improved. I think that It will bo admitted by all that rain Is the primary cause of our roads geitlng out of order, from the fact that it soften t the roads; from this. It will be clear that everything that can be done to obviato the settling of ruin on the roads isossentlal to their durability. I entirely agree with Sir Joseph Whitworth's remarks, as quoted in the Enolish Mechanic of March 11. Tbe barbarous mode in which our roads are mended is beyond all comprehension. What is the cause of the uuinerous holes (which are so ninny lodgments for water) on some of our roads? I was under the Impression for some time thatit was entirely owing to a weakness in the foundation ; it may bo so in part, but I believe the cause Is also, and moio probably, owing to the crossings of the wheel tracks before the rond is set. If a pool steam roller were used immediately nfler repairs, nud the road set or hardened, we should not luive such holos and unevenncsa ns; ito our disgrace) Is so common In thtse enlightened dnyB.

But, I fancy I hear a road surveyor say, But what of tbe expense? Who Is to Hud the money to repai r tliein in that expensive way? In answer, I would say, going on with the preseut system of repairing our rouds Is carrying out the old maxim of being penny wise and pound foolish. I my, repair the ronds in the way suggested, and I believe in a short time It will, perhaps, not take half tbe expense to keep thein in good order.

I have adverted to tbe subject of roads because It Is
so intermingled with tbo subject of velocipedes that
the one can not be divorced (rum tbe other; iu fact, the
velocipede question is more a question ol road than
one of mechanics, and I trust that very soon wiser
counsels will prevail with those to whom we look for all

firogross in this respect, and I anxiously hope that, ere
ong, the ronds of this kingdom will be in such a
state of excellence as greatly to eubance and en-
courago the use of that most noble machine, the
velocipede, which, rightly used, tends so greatly to

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A. Centre pin, holding front axle.

II. Front axle, 30lu wide outside measurement. ». the front

C. A block of wood to raise the plank 2lln. from the ground, as the front must be 3iu. higher than behind.

F 8rnugcn<f forkdto'hold steering handle In its place when going down .111.
X. Ash plank, 4ft. 3ln. long, 8ln. broad, 2in. thick.

All velocipedes require good steering which Is only acquired, by practice. This machine is constructed uo'n the principle that the driving wheel shall :bear all the weight ot tbe rider, so that the front wheels are only needed to steer by and hold the frame steady No springs are required, nor is there any Jolting-. If the front axle is taken away and a small steering wheel put in Its place, it would lorm »«"»;"» bicycle, which could not upset, because the levers would catch the ground. Thos. Stakwat.

THE FIGURE AND MOTIONS OF THE EARTH.
THK* -THE EARTH'S ROTATION.

Sir —My object In writing a series of letters on th Is subject is not to establish any new theory, but to so far combat old ones as I deem (aud I trust I shall show) are not founded on fact, but are called in to existence from necessity, as an aid, to some extent, in establishing other theories. I think no one will de ny that any theory not founded on fact is injuriousIn ao far as it not only takjs the place of what is in accordance with fact, but by a cursory examination tends in some measure to confirm or represent error as truth and so far is positively injurious to the best interests

°Yproep'osle with your consent to alter the form of my succeeding remarks on this subject from what appeared in tbe English Mechanic, Vol. X, page jlO, and propose to consider the whole matter under the separate heads, Rotation, Revolution, Parallax, and Gravity. These subjects are so bound up together by the modern system a» to be absolutely Inseparable one from another: And In connection with these subjects I also propose to notice Mr. Proctor'o arguments on eaoh as I proceed, as I deem this plan more precise and better connected, and of course will be better understood by the majority of your reudera. I will, therefore, without further prefatory remark, procoed at once to uotice the Theory of the Karth s Itotat Oil

We are told by modern astronomers that the earth is nearly SHOO miles In diameter which being multinlied by 3 1416 gives an equatorial circumference of 25132 miles, whicTi (performing one rotation every 24 hours gives a surface speed of 17 miles per minute for any object oS such surface, but continually decreasing as we approach the poles. Our Arctic voyagers so far as I am aware, say nothing about per«e,vi,,g any di ference ns tboy approach tbe Arctic Circle, as it is caUed If, therefore, we examine this theory-closely and assist tbe elucidation by a diner* n, we shall ttud the whole Idea to be simply absurd

LetN represent the north, Bnd S the south pole. It

< "■' gal force at tbe equator

A It must be proportionately greater then it is at C D, aud would amount to nothing could we )esc'„ the poles themselves (X or ti,. Thus, while a body on one part of the earth's surface is rushing through space at the rate of 17 miles per minute, a body ou the polar surface would be stationary, or nearly so; a matter it la necessary to prove before we can correctly say that the earth rotates about its axis, as it is said to do.

We will now examine the consequences which must nrise from this extraordinary speed through space. Suppose a»person ascends In a balloou on a calm day to a height of three milts, and remains at that altitude for half-an-hour, be, instead of descending where he promote the health of our people, to give vivacity to went up would be left (17 x 30 =) 510 allies to the society, to add vigour and stability to the Stole, and west, that is supposing no current ot air existed at tuc

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to bring honour aud glory to our country.

I thank you for the vast fund of Information which 1 from week to week receive, and do from day to day

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miles, and If he remained up one hour, to E, or 1000 miles, aud Bo In proportion to the time hu remains suspended In the air.

1 need hardly Ray this la not so, and the idea is only tenable on the'grouud that the atmosphere in iuseperably connected with the earth, that the atmosphere moves with the rotating earth at the same speed and in the same direction -, but I am not aware that it haw yet been proved to do so. How can that which flouts on its surface from all points of the compass be said to be a fixture and invariably move with it?

But the double motion of the earth, that is its rotation about its axis, and its revolution about the sun upset* this arguineut eutirely, for if the atmosphere is a fixture considered iu connection with the earth's rotation, what is to become of its fixity in connection with the revolution of the earth round the sun, at a speed at which I theuld think even Mr. Proctor stands aghast, and which I shall eventually show Is a manifest absurdity—au utter Impossibility.

Even the commonest observer must know that much of the strong wind we experience In this country at certain seasons of the year Is from the west, that is in the same direction as the earth's rotation, and suppose the day on which we make our observation is a stormy one, he will And the clouds carried past him at the rate of from 50 to tiO mileB per hour, or near one milt* per minute. But the earth is said to bo acrompiinktl in its* rotation at a speed 17 times as great as our storm clouds by the air in which these same clouds JtiKit; how can this be? If it really is so, the clouds must be travelling at a speed of 16 miles per minute, inasmuch as they rush over the earth"s surface at a speed of ono mile per minute, while the eanh rotates at 17 miles per minute, which together make 1H miles in one minute of time.

Again, if tho earth rotates from west to cast, and a storm comes from the south at a rate of one mile per minute, and the peaks aud valleys of the earth's Burface are parsing at a speed of 17 miles per mluute, what would become of us? The centrifugal force generated by the earth's rotation and the wind would cross each other to such an extent as to derange the whole order of creation; the effect must be precisely the same as of two bodies striking: each other at opposite angles.

If the atmosphere is really a fixture in connection with the eanh in its rotation about its axis, and that both proceed from west to east at the speed just named, how shall we explain away the first and most simple principles of motion? A railway train would not be able to proceed at the same speed from east to west as from west to east, because of the current of speed assumed by the earth in its rotation. For instance, if any one will try to alight from a railway train when in motion, he will find he must alight by springing- in the direction of the motion of the train, or he will be brought to the ground, which would be a certainty if he had the temerity to leap in the direction of the rear of the train. This principle holds good throughout all nature. If two objects connected In motion in the same direction are not impeded in any shape, one communicates an impulse to the other in the direction of motion ; but if they oppose each other, then, as a matter of course, the superior weight and velocity in the oue direction will act as an impediment to the full force in the other.

If the earth d»es rotate at this fearful speed, what becomes of the centrifugal force which must bo called into existence at the equator (and proportionally as we approach the poles;? This force is a universal principle in the circular motion of all bodice Ih proportion to the extent of the path traversed mid to the Bpeed exercised. This being the case, a tendency in all things to fly from tho surface of the globe is manifest, and it is here where gravitative attraction steps in, as it were, aud presumes to settle the difficulty by applying a power controlling this centrifugal force by a power 17 times as great as the centrifugal force existing. AVe shall see when we conic to examine the theory of gravity, at what an erroneous conclusion its supporters have arrived. The centrifugal force not being called In question, except as its beiug controlled as above, it need only to be further said that independent of thisgTavfty no living thing could exist, excepting, us I have before shown, near the poles.

John Beardsley.

(To bd continued.)

discrepancy betweeu the work performed by the one stop and the work performed by the four stops ; although the grand jeuprofesses to accomplish as much, it fails to do so. An attentive examination will show the cause of failure to be that whilst the " grand jeu" opens the four valves. It omits at the same time closing the four little escapement valves. Thus it is that the wind escapes so fast that the blowing becomes hard work to meet demands both of u*e and waste. Why, then, are the escapement* Ineffective? Because tho large valves are not sufficiently depressed to let the escapements fall and set close over the apertures they ahuuld cover, bo we arrive at the cnusc of the defect—namely, that the. poker or sticker worked by the grand jeu is too short. Insert one that shall be of suitable length, and it will perform its work, giving1 results precisely the s,\rae as the four stops lor which it is Intended to be a faithful substitute or deputy.

Iu reply to question of "J. H." on same pag"e. Rivets for harmonium tongues are not of English manufacture; would be obtained only by order from abroad. They are needles**, for a yard of iron wire will answer for the purpose of amateurs1 practice. Manufacturers find it much cheaper to buy reeds than to spend time nu repairing them.

For tuning harmoniums ("Vibrator," page fifl) there 1b no royal road. It Is tedious nnd laborious work. The practised tuner, however, docs not open the instrument to each reed, he ascertains what, half a dozen or more reeds will require, bears in mind which will want flattening, which sharpeuiug, and the degree of each, and with the catalogue on his tablets of memory, be rectifies the lot, at once opening the instrument, and by habit he can so work with comparatively few discrepancies in results. The finer touches are given in a final survey of the whole.

Fitting up tho case of a single row harmonium, as required by "J. W.," page 21, in order to accommodate two rows of reeds, will be a vety troublesome affair, and to carry out the design, securing at the same time the proper working of'the mechanism, will be a trial to ingenuity. The size of case must be stated before a definite opinion can he pronounced, and another matter of consideration will be the size of bellows, which it appears are already made, for it will be useless to have two rows of reeds unless there Is a provision for wind supply equal to the amount required for their speech under full play. A sound board for two rows will measure at least ten inches in width with utmost paring down of frame; oue made eleven or twelve Inches will glvo a better character, and more fullness of power to the lfift. tone. The two sets of reeds are said to be respectively of 8ft. and 16ft. tone, the latter being an octave deeper in pitch than the former, and especially desirable lor sacred music.

"FetderB," concerning which " W. D.," page 21, makes inquiry, may be placed at bottom of case, that is to say, in horizontal position, that the feet may act directly upon them without intervention of levers for working. In some small Instruments the plan Is adopted, but it Is not a desirable oue for larger fixes, as tho command over the wind is restricted and not easily managed. By leverage we can moilify the extent of throw given to tho feeder, and regulate the stroke to the pressure, considerations of importance when a large supply of wind is in requisition. Hermann Smith.

1\S —Pendulum. I notice a statement by *■ Catseye Diamond," page 4-1, on the sympathetic vibration of two pendulums; if the pendulums, however closely hung, are attached to different supports the same manifestation will not arise. I*rofes»or Leslie has shown that the vILration is conducted between the points of attachment of the two pendulums, it passes along the fibre of the wend or metal rod, a phenomena quite distinct from tlw sympathetic vibration of strings excited by the medium of air.

HARMONIUM REEDS.—PENDULUMS.

Sin,—To several questions on harmonium matters, I have the pleasure of giving replies.

A few words will solve "J. H. C-'s" difficulty {page fly), and will probably be useful to others, the delect he states being oue of common occurrence. Theiustrunient named lias two rows of vibrators, consequently it has four of its stops acting directly to give speech to the vibrators or reeds; these we call register-stops. Every instrument ought to have an ample supply of wind for Its requirements under the play of the fullest harmonies. The first point to bo decided before testing the •' grand jeu " is the adequacy of the windpower when all the register-stops are drawn. We will assume this to have been ascertained in the affirmative. The "grand jeu" Btop acls by interior mechanism upon the same valves that are acted upon by the exterior apparatus of the several stop-rods and levers; the defect Is not in the wind, therefore, it is in the nitchiLuiam actuating the valves; there must be some

SEWING MACHINES.—I.

Sir,—The history and development of tho sewing machine are subjects of great interest to the mechanic. No other machine of recent years has stimulated the inveutive faculty and the application of mechanical skill to a greater degree. It has employed a large amount of capital and skilled labour with great and deferred success, and it is likely to continue to engage the attention of Inventors, capitalists, and machinists for some time longer. The failures have been so frequent and numerous, that they are well known to the trade, which, indeed, often evinces gross and culpable Ignorance of mcchatilcal principles.

Some, who are uuable to invent or improve, but who are fraudulently desirous to take the trade, from deserving inventors and patentees, have offered lor sale worthless imitations, which have occasioned great trouble and expense, not only to themselves, but aleo to the users of their useless productions. It is a remarkable thing that some people, who think it criminal to steal a pound of brass, will not hesitate to take by fraud what is worth more than a pound of gold -that which was produced by the hard and honest exerel«o of their neighbour's intellect. Rut, as the terms of some of these patents have expired, examples of the several classes, with descriptiuus ami drawings, will be given Iu these pages, so that even the amateur mechanic may b«enabled to make n sewing machine, and tind ample scope to exercise and display his' mechanical skill.

The sewing machine presents an extensive field of inquiry to the student of mechanical appliances, exhibiting a greater variety of wavy to effect a definite object than can bo observed in engines, lathes, or other similar structures, which, it U well known, have had longer time and more experience to be brought to perfection. The readers of the Ksglish Mechanic who have the advantage of contributing toils pa^es inny sometimes employ their scientific acquirements In exposing popular errors, and showing the merits or detects of the various species of nuvliig machines, rrid thus in some measure contribute to tho welfuro and pleasure of a numerous and deserving class of their toiling brethren, by rendering tbeir tanks more fnHkand agreeable, aud preventing thclrriliuiou of lumper

and dejection of spirits, *e., whleh too frequently arise from the use of Implements ill-constructed for their purpose. Communications in these pages of scientific and reliable information respecting sewing machines, from persons having no self-interest iu tho sale ol them, may, while they advert to their comparative merits and defects, direct purchasers to the best system of construction, and so prevent poor people from beiug imposed upon by the delusive and exaggerated statements of unscrupulous vendors, who represent their own frequently worthless things as superior to all others. Thus, for many reasons it is desirable that the English: Mechanic should take up this subject, and furnish in Its pages practical and reliable information, which may be referred to as authoritative in the making and using of sewing machines.

This would seem to be a step in the right direction for technical education, and thus many being enabled to avail themselves of the aid and experience of intelligent practical and scleutiflc men. may make successful efforts in improving sewing machines, which may greatly lend to their own and to the public advantage. If some of the workmen who evince decided talent in the construction of these machines could be encouraged to study and to excel in their business—if they would derive their pleasures from Instructive books. Instead of from demoralising drink—their own mental and physical powers would be improved, and I havo no doubt that the sewing machines and other mechanical inpleiuents which they would produce would manifest a corresponding improvement, and so may become more conducive to the pleasure and profit of all who use them. Working- men may ask how it is that wo cannot keep out foreign manufactured sewing machines We tak' from America alone to the valao ot upwards of £200,000 annually, a sum that would employ IKH> men at home in comfort, Instead of roughing it In the colonies. We have a position, and the raw material at hand, the most convenient to make sewing machines for all the markets in the world, and ought to employ an additional 10,000 men. Our merchants would do their parts in pelling. What is the .reason we do not make? If it is simply excessive taxation, let It be discussed elsewhere ; "hut If the misfortune be due to workshop mismanagement, it ought to be debated in these pages, to the ultimate benefit of employer and employed.

There are many sorts of sewing- machines, to produce Btitching of various qualities-some for ornament, some for strength, some for heavy, some for light goods. Some machines are very difficult to be learned and kept In order, although an experienced teacher may prevent much of the trouble from arising1. In some there Is little difficulty to learn without a teacher, a few lessons from printed instructions beiug sufficient to enable a person to do common stitching in a few hours' practice. Some machines, the most difficult to be learned, amply repay the patience bestowed in acquiring a thorough knowlego of their working, and in the course of a few yoars confirm the truth of the adage, " A stitch in time saves nine," aud thnt a good machine stitch will save ninety-nine. All the machines in common use make the one-thread stitch or the two-thread stitch. The former works thread from oue side of the fabric, the latter from both sides. On the top side the stitching i* nearly alike in all tho machines. On the under side the onethread machine forms a loop, and iu a few machines a half-twist is given to tho loop. One clasa of machines I uteri ace the two threads on the lower side. All these chain or loop-stitche* will ravel out by pulling the thread from one end, but the two-thread stitch is more elastic aud durable than the single-thread stitch. There are two classes of machines which make the lock-stitch. Otic carries its thread from the reel in a shuttle through the loop ot the needle or upper thread. The other lias its thread wound in a spool, and a rotating hook lakes hold of the needle thread, and carrier it around the spool. Forstrcngth aud beauty, and command of stitch, tho shuttle is the best system. The spool machine makes the least noise, and is very rapid, which advantages over the shuttle machiue were at one time very great. The spool machiue has undergone the least alteration, but the shuttle machine has been Improved so much that it scarcely owns its parentage, except in tho original movement of needle aud shuttle. By reconstruction, tho other parts, in some of the modern machines, nearly equal the spool machines In their quiet and speedy action. The quietness of the spool machine ts very much due to the use of a curved needle worked by a rooking lever. Tho curved needle is more expensive in the first cost, and more liable to break than tho straight needle. Tho nature of these sewing instruments (which will be subsequently fouud by a person studying them to vary nothing in principle) having been described, it will then be requisite to give patient and observant attention to the formation of the variouB stitches, and to the action of the Instruments in the execution of each distinct sort of stitch. This being thoroughly done, the student will the more easily acquire tho knowledge of a variety of constructions to be benmf ter presented to him In these pages.

A Practical Man.

IJIU HEADS, BIOLOGY, AND MATRIMONY.

Sin,—There is a time in every man's life when ho acta foolishly; some do so, discover it, and Improve, others do not seem to know ft nor acknowledge it. Of the latter there l« little hope of improvement, and of these two classes the world appears to be mnde up. 1 have been a reader of the Engt.isii Mechanic foi some time, aud have been so pleaded with the gradual Improvement it has made, that 1 have introduced it to my workpeople.

When your correspondent " Disc " asked how it was that one person has Influence over another in mesmerism mid electro-biology, seeing that no one replied. I gave what 1 believed to be tho proper answer to hi* question and which has not yet been refuted-but a heap of nbu«e was east upon mo Instead Fifty suminrr-t have passed over my head, and I am yet a learner, ami not ushamed to acknowledge it Experience has taught me that tho man who abuses yon brviuiHo you differ from him Is not the man that society can look to for improvement. I name this, knowing abuse miirht follow from those who know Ht(l« of the subject they oppose. Three letters appeared f lie week after mine, iu reply toil. That of "Suburban" is candid and respectful-, thoie of "Saul Ryinoa" aud "AmiHuiubuir," do ihem uo credit.

that others are preveotod ftom contributing to your uninll brain. If wo rslcr «ize as a measure of power, journal. believing from the spirit already shown that ! then we must submit that lu each head the large

In reply to " Saul Kymca," I beg to say a moment's reflection would have taujjhi him the folly of his argument. If Lord Peuxance was a practical phrenologist, it would have made no difference, a> his duty is to administer the law, not to alter it. "Saul " further •ays that all clergymen should be practical phrcuologi*W by Art of Parliament, thus inferring- that an Act of Parliament can give a mun brains, because, If all «lergymen could be made so, a thing1 impossible, they could not prevent foolish and unequal marriages. A man nviy preach a good sermon, aud yet not have the ability tor a good pnrenologist.

All prioress is slow, whether to geod or evil, and those unfortunate people who have to appear before Lorl Penzance do not come suddenly to the unfoitunate position they are hr >ught to, but are led from bad to worse, from a look to an act; and it la for ** Saul Rytnea " to prove that the attracting and repelling influence referred to in my letter has had nothing to do with bringing: them into this unenviable p> eitlon, and causing them to seek associates more congenial to their feelings and passions.

I still believe, whatever may be said to the contrary, that if young people were to follow the advice of a practical phrenologist, much misory would be prevented and fewer would separate. Here we have a married couple; did they live In love and harmony previous to their coming before Lord Penzance? If they did, why seek a separation? If they did not. let the cause be traced to its origin, and you will find that ultcen out of every twenty were never suited for each other. One thing is certain, where husband and wife live In love and harmony, there is little fear of their disgracing themselves with those crimes that bring people before- Lord Penzance.

"Antl Humbug" knows it woman who has a drunken husband, who beats hc-r, and because he does Bo, he thinks my arguments do not stand good. Pray, what has tbts to do with the subject? I was not writing about fools and madmen—I can look upon drunkards as no better. I have heard it said that two-thirds of

organs will have more power than the small out*; and
although two brains may be equal in size, one,
from posses sing ;i tiner texture, will have a more

ffowerful constitution than the other, always kcepiujj
n mind the temperament, which, as "Mgma " justly
remarked, is the key to the whole secret. The tem-
peraments are distinguished, of course, by the coun-
tenance aud general formation of the to'ly. This will
give an index to tho natural qualities, and will be a
guide to those who intend to atudy this Interesting
science.

In most cases, a person with a large brain and small
muscle will naturally incline moru to mental than
muscular labour, whilst :t person with a small brain
and large muscle, if of a bilious or sanguiue tem-
perament, will incline to exert himself mor* In bodily
labour. These remarks of course have reference to
healthy bruins, as the brain, lite the body, may bo
diseased, and yet not lessened lu size, but rendered
almost, if nut altogether useless,

1 make the fun-going remarks respecting large and small brains that my words lu a former loiter may not b« lui.-iuuderstood. I now conclude, by advising young men to read "Cobbett s Advice to Young Men, especially his " Letter to a Lover." His remarks, though amiuiug. are Interesting aud really u-iful, aud will be found not fur from the mark. My time being taken up with business matters prevented this appearing sooner, and as before stated, beiifg written amidst tliu noise of machinery, and at intervals, your readers will have to take It for what it Is worth.

T. D.t Workiugtou.

an author,' &e. I Bee witb pleasure thai a ' F.R.G.S.* intends to send some accounts of the proceedings of his society. 'this would be much approved of by mauy readers, and aid to the popularity of the paper. A suggestion was also made last year—I repeat it now—the number of re ders being much Increased it might find more echo-, it Is that when a new praJuee cornea somewhere on the market, one or other reader might raeutiou it in the paper. He will be sure always to give or to receive information."

REPLIES TO QUERIES.

EXTRACTS FROM CORRESPONDENCE.

MR. IIIGG8 ON* ALGKIUtA.—"Iliiffo" writes:— Mr. Iliggs asks ine, ou page &>, why he used the radical sign? 1 have not the faintest idea why be did *u; ho might just as easily have Inserted the actual square root of 17.*>, at leant up to a iVw places of decimals. He has not taken the square root of the exprcs_ slon in question, for that is impossible: but ho has

the men who turn drunkards after they are married i certainly attempted it f must still, then-fore, beg

are made so on account of the unsuitabieness of bus- | him to Inform the readers of the Knclish Mechanic

band and wife. I will not liBzard this assertion. | how ho hud * that

although i believe there are many. That the human

body contain-? an attracting and repelling power I have no doubt, call it by what name you like; 1 call It negative und positive, and iu tnis 1 am borne out by one of the first authorities of the day, Dr. J. II. Dodg, who first discovered electro-biology, or as he calls It, "Electrical Psychology, or the Scleuceof the Soul." The Doctor was twice invited todeliver those lectures before the American Stnvte. Many years before I knew anything of phrenology or mesmerism, I proved to my own satisfaction that the human body contained au attracting a%d repelling power, aud was astonished when reading the above author to find that he not only bears me out in this, but clearly proves in his lectures that the body does contain negative and poeitivo poles. The work may be had of Twee lie.

175

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I will not occupy any more of your truly valuable space further than to express a hope that such statements as this will not find a place in Mr. Biggs' notes on algebra."

MACHINERY VERSUS STEAM.—"A Clerical Subscriber " writes :— "Muuy small engines are now made to work by clockwork. Why are they not made ou a larger scale? What is doue on a small scale may be done on a large one. The beautiful adjustment of a modern watch may be introduced into a locomotive; greater safety would be obtained, enormous expense saved, and coals delivered to the poor at

Mniuil. Loadoa. I give a short extract in the Dr.'s 4b. a ton; besides, in the case of steamers, they would

words. Ju speaking of the Fowlers of New York ni;d Georgo Combe, ho says, ou page 44:—"They have inade n righteous dovelopement of true character in toe phrenological examination of thousands of human heads; have directed the auxlous parent how to train tip the child of his affections; have pointed out to the signing lover bow to choose a congenial spirit of companionship for life; and have poured the light of mental and moral improvement in silvery stream? on the -rami Koipire of Hind, yet such a science as this has been called a humbug." Again, on page 54, the Dr. continues:—" It will be readily perceived hy everyone acquainted with electrical science, that if I can flud an individual standing iu a negative relationship to myself, or by any process render him so, then 1 beiu" the positive power, can, by producing electrical Impres" atom from my own mind upon his, control his muscles with the most perfect ease. This is evident, because tbeptmtiie and negative forces electrically and magnetically blend, are equal In power, and paralyse euch other ; or, ou the contrary, produce motion." Again on page 100, he refers to the negative and positive forces in man, which is loo long to copy here.

I have for some few years back paid attention to medical galvanism, and often found, when applying the battery to different parts of the body, that the influence which I intended to produce was counteracted, and when the poles were reversed, the influence was also reversed, thus clearly proving that the body, as well as the battery, coutains its negative ami positive poles. Another proof that will bear me out and which f think equally as strong as the last : it is admitted by scientidc men that the ntrnospherc is charged with positive electricity, and the earth, as well oa the food we consume coming from the earth is charged with negative electricity. If you sit in a current of air, with your back to it, you arc almost certain to catch a cold, but if you turn your face to it there is not so much danger. Again, when out in a cold day, we instinctively cover the back part of the neck, and leave the front part bare, there being an attracting force between the back part of the neck and toe atmo*phere; wo feel the cold more keenly in the neck, whilst the face throws it off, ns if containing a repulsive power. Surely with these proofs so clearly before us It is too much for any man to say I am talking nonsense; if so, the author above referred to has wrilteo a book full of nonsense, but it is such as will stand fnveitigatiou. Your correspondents try to make it appear as if I was led away by big heads, or large head*. If they will kindly refer to my letter, they will find no reference whatever to large heads. I mentioned large brains as taking the lead; i should have qualified it, but when I tell you that my letter was written amidst the uolse of machinery, it will, in a measure, account for a sUghlerror, which otherwise would not have occurred. The vara; four kingdoms, should be kingdom.

That I may not be misunderstood, permit me to say that 1 endorse '• Sigma'a" description of large and

always be independent of fuel by the change. "It may seem Improbable, but wo must remember the derision witli which steam was ushered into existence as locomotive power."

SPOT3 ON THE 8UN.--G. C. C" writes:"Some of your readers may not be aware that II iseisv, with any good opera-glass, to see distinctly (though not, of cuurse, forpurposcsof scientificolxerv.itioiu the spotson the sun's surface, by>imply taklngmittheupper or lower pair of lenses, and blackening their Interior surface over tho flame of a caudle. Several spots are now visible, and a great change. In their relative positions may be observed, not ouly from one day to another, but If looked at at different hours on tho same day."

THE ILLUMINATED TOKTION OP THE MOON. —Mr. John Beardsley says :—" I had overlooked the letter of 'It. L. J.,' In No. 301. until a friend called my ntteutiou to it, aud although 'It. L. J.' says my 'diagram helps to prove "Sigma'e" views iustead of my own,' ho fails to show how it does so. My argument is that If he extends his thread not ;i.lft only, but If he could for :u,ooo.o uft., he would ucvor And that the plane of such distance would be truly parallel to the higher object, simply because, as 1 said before, the further be moves from the object tho less will be tho angle formed by moving a (riven distance, until sueli angles would not even be d'wernihte.

DIGITALIN.—"Pharmaceutical Student" writes:— Many thanks to tho gentlemen who have replied my query respecting digitalin. I thank Mr.

to

Godfrey for pointing out my error: and I thank
"K. K. "for his kind suggestion. I vaporised every-
thing that was volatile at 212° in vacuo, air pump
constantly going, until not another but.Wo would rise.
No heat was applied afterwards except what it received
from the warm acid acetic solutlou. Amougst our
readers who take an interest in'pharmacy, uud who
have attempted the extraction of the less stable ba-cs
(the isolation of which I believe to be extremely
difficult), will they favour me with their re«ult, as I at
present have but operated on the more stable? 1 had
been successful till I was brought to u halt by digi-
talis, in theory I have a universal process for the
extraction of alkaloids. I should be pleased to submit

rioIl.]-APPABENT PARADOX—" Excelsior" objects to my explana:ion, ou the ground that 1 have "confuted division with multiplication." He must excuse me if I do not see it. The error certainly lies in botli sides of the equation being divided by a -6, which by hypothesis c o. No other explanation Is needed for a mathematician. Ky-tbo-bye, is the term "paradox"properly used in this case.' Is it not rather a' ceirtradietiou"? —Pnf.uma.

[1830.J-ASCIIALTE VARNISH.—This can be made by belling common coal tar until it shows a disposition to hardeu on cooling; this can be ascertained by rubbing a little on a ;->iece of metal Then add about 20 per ceut. of lump asuhalte, stirring the same with the boiling coal tar while melting therein, until all the lumps are melted, when it can be allowed tocool and kept for use. This makes a very bright varnish for sheet metals, and very cheap and durable. Common coal tar will not dry readily, as it is not properly boll-.'d to expel the volatile hydrocarbons, which prevent its drying. It should bo boiled out of doors, as It might take Are uud burn tho building.—American Sub

flCRIBER.

[1970.]—VARNISH FOR IRON PATTERNS.—A good varnish for iron is made as follows :—Take oil ot turpentine and drop into it, drop by drop, strong commercial oil of vitriol; tho acid will cause adark syrupy precipitate lu tho oil of turpentine; keep adding drops ot vitriol until tho precipitate ceases taking place, theu pour out tho liquid and wash tho syrupy ma-s with water, and it is ready for uso. lleut the Iron to bo varnished to a gentle heat, and apply the syrupy product and allow It to dry; it will be found, on being dried, that this varnish has become incorporated with the surface of the iron, and therefore very purm.mcut and durable—American Suiiscriuer.

[21671 — LATIN. — Get Dr. Smith's "Princlpin Latlna,' Part I; Murray, price Its. 6d. Carefully learn each vocabulary a day or two before writing out the corresponding exercise. Learn the declensions and conjugations thoroughly. Make a practice of dally decliuiug or conjugating ono or more words, and by coutiuued application •' Keader "will soou be able to get a fair knowledge of tho language.—C. II. W. U.

[«180.]-KNGIM£KKING IN GERM ANY.—For the benefit of " Y. P. W.," and others, allow me to make an extract from an article by H. I-'. Koscoe, in Sature. He says—"As a typo of this interesting class of science schools, I may cite the two celebrated schools of Carlsruho aud Zurich, beginning with the Cat isruhe school witli its ouu students. In the original programme, the school was declared to oonsist of one general aud sewn special departments. The general department, called the Matltcmu'ical, furnished instruction iu mathematics, iu natural science, and in modern languages and literature." This programme has been slightly altered, uud now the schools are as follows:— Duration of complete course—1. Mathematics, 2 years. 2. Civil Eugineoriug, 24 years. 3. Mechanical Engineering, 2 ytuirs. 4. Architecture, 4 j ears. 5. Chemistry, —. 0. Forestry, 3 years. 7, Agricu'ture, 2A years. In Zurich exist both a University aud a Polytechnic School, and although the university is a Cantoual, and tho school a Federal institution, they are so far allied that they share one magnificent building, ond many ttudents of the uuiversity are, at the samo time, pupils iu the school. The most important department of tho Polytechnic School is that of mathematics and engiueeriug. The following extracts from the prospectus of the lectures iu the Engineering Department of tho Zurich school show how much more complete is the scheme of instruction theie than has at present been found possible in England, ii. Department of Civil Engineering (duration of course- :!J years). 1st year— Differential and integral calculus, descriptive geometry, priuciplesof construction, practice ill construction, drawing, experimental physics, experimental chemistry. 2nd year — Differential equations, technical mechanics, geometry of throe dimensions, perspective, technical geology, topography, drawing, descriptive mechanical construction, surveyiug. :;rd year—Theoretical mechanical construetl.iu, astrouoray, geodesy, construction oliron bridges, railways and iron roofs, drawing. In addition to these courses, there are similarly extensive programmes for the other departments. The expenses are small. At Zurich, any of tho regular courses of the distinct departments or schools, can be attended for the payment of 10U francs, or about £4 is. for the session of nine mouths.—C. H. \V. B.

[2200.J-OVERLAND ROUTE.—If two letters are posted to India, the one via Southampton would proceed from that port by a ship which would cuter the Mediterranean by the Straits of Gibraltar, and land her malls at Alexandria. The other letter, riu Marseilles, miirht be posted in Loudon six days later, and transmitting all the heat rays. He will find H great Improvement II he gets their revolving mn glass, with 4 different colours. Of these, the '"London smoke,' No. 3, will enable him to look at the sun for hours without the trouble of a second gl»s«. But the grandtBt views I have had of it have been with the 2 day eyepieses ; these give the best Idea of its size, nnd'wblleshowiugthe penumbra and faculie, &c,give n magnificent bird's-eye view of the whole mass. For these I have had a dark glass of "Londou Smoke" made by cutting out the brass of the ordinary day eyehole, leaving only a narrow rim lust sufficient to hold the glass, so that the end of the tube is all class. This answers admirably. Free by post 7». The revolving sun-glass, also adapted for Venus and the fullmoon.ls 10s. Ad.; both valuable additions to the lelescopc; thela»t will screw on the astro-eyepieces only. With this telescope I can discern easily the3 doubles of Orion's belt—a severe test — Amateur.

It to the notice of brother students. Is there any I would go by Dover to Calais by packet, theu by rail to work devoted to the extraction of the vegetable | .Marseilles, and thence by ship to Alexandria, and so 1 '' '■''" »'- """•- '"""- The extra threepence is well

bases?"

SUGGESTIONS. Ac.-" Henry II., Namur, Belglum," eayB:—"I am happy to see the continued success of our English Mechanic, and must tell you uf tho several satisfactory letters I have received from my friends to whom I had recommended it. I had the pleasure to procure ft good number of subscribers, also some new contributors; all see with the greatest satisfaction the continued improvement of your publication. Recipes should bo followed by the words 'tried,' or 'proved,' or 'extracted from such

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earned by the delay of six days and the extra troub -F.K.C.S.

[2338].-SOLUTION OF PROBLEM.—On p. 41, No. 202, for hypotheuuse is divided at " 8," read at" D."— Bernardin.

[223l.]-COLOURED OBJECT GLASS. — I can second whnt your correspondent says respecting tho excellence of Solomon's telescope. The red glass scut with It is not sulticicutly dark; in fact, 1 Hud it impossible to use red glasses, as they are so burning hot

[2270.}—MOTION OF WATER.—J. Croinpton does not state enough in his query to bo able to give a very definite answer. If the hole is through a thin plate in the sido of a cistern or pipe, 5800 gallons'per hour would pass through it, or about 929 cubic feet.— Q, Q R

[1270.1 -MOTION OF WATER.—J. Cromptonmust particularise, in order to get a correct answer. Is the orifice lu the form of the renn contrarta, and what thickness is the plate in which the hole is bored; this latter will nltcct the vena contracta. and consequently the quantity of water discharged. If J. Croinpton has .181b. ;pressurc per square luch, his head of water is equal to about 8.Vf>fi., which would be valuable fur many purposes, even with a quantity of water sufficient to Bupply only a pipe llu. in diameter.—Senex.

[2273 ]—TELESCOPE.—Dr. Kitchener's Iclesoope, known by the name of the " Aubert," was advertised for sale in the Athenamm of Feb 9, 1861, price £130, by the Kev. A. F. 1'adloy, Lincoln. This is the " Beauclerc Object Uiass," moutloncd by " G." What became of the Doctor's other telescopes 1 do not know.— G. J. W.

r2275.]-SUN GLASS FOR TELESCOPE—J. H. Ward will find tho beat glass for viewing the sun to be the neutral tint wedge, made for that purpose, and ■old by the opticians. Or he can try suah combination of common coloured glasses as will give the nearest approach to neutral tint, avoiding deep red, which seems to blot out detail. I Hud purple, green, and blue, cemented together with o)4 hard Canada balsam (melted, and the glasses made hot), avoiding air bubbles, to answer very well, allowing the mottling of the surface to be well seen. Strip*. 2in. by llu., with an extra thickness over half, in case the oilier should not be sufficient to prevent the light being uuplcasant, or combinations with different shades of the same colours, might be desirable—S. B.

[2275.]—SUN GLASS FOR TELESCOPE.-Any coloured a lass, sufficiently dark and clear, may be used to view the sun, or even a piece of smoked glass. More costly eye-pieces for this purpose are made by optician. If no other protection than coloured glass is used, the observer should contract the object-glass to 2ln., or he may Injure himself very seriously. Throwing the Image of the sun on a sheet of white paper, held at a proper distance before the eye-piece, is not a bad plan. -G. J. W.

[2382]-POWER OF STEAM.—The 32ft. length of steam pipe will not cause much loss of pressure if the pipe is well covered and protected from condensation, providing that the pipe is not of a very small diameter, as then the friction would be sufficient of itself to reduce the pressure materially.— Q. Q. R.

[2283.]—PAINTING SCENES.-Tho best way to paint theatrical scenes is, 1st, to sew the calico to

f ether, 2nd, melt some glue so that it will be ns iquid as possible, then mix the common paint used with oil. with it paint the scene and leave it to dry for about one hour. It won't cr ack, and no varnish need be uaed. — II. Garland.

[2200.]—BROAD PENCILS.—Wlnsor and Newton sell the pencils with broad oblong leads.—G. E. Crick.

[am]—THEOREM.—In answer to " E. W. V.," I

[graphic]

would sav, let him make an ellipse, the circumference 3 + 2

of which is + 31410 = 7-8540 area = 3 x 2 x

2 7856 = 47124. Diameter of circle with same per. - 2}. Area of circle = 2J 3 + : 7854 = 4 1)1)8730.—

W. STEPHENSON.

[22%.1-COPPER DIK.-Takc a piece of clean copper, and having heated it to a blood red, place it iu a strong iron ring on the anvil, and hold the dloovor it whilst au assistant strikes a blow with a sledgehammer. The copper will be found to be an exact counterpart of the die. If this has been carefully aud quickly done.—Chip.

[2!96] -MONOGRAM DIE.-" Cantab" will find it the best p'an lo electrotype his copper counterpart ou his steel lie By- thu-byc, this counterpart has strangely received the inlsuomer of a "matrix," which term obviously belongs, of right, to the sunk die. —F. It C. 8.

[2290J-MONAGRAM DIE.—The copper matrix is not cut, it is stamped or cast.—Iota.

[2207.1- VIOLET INK.—I forward two recipes for "Cantao's" benefit:—1. Boll Soz. of logwood in :i pints of rain or distilled water tolt pint; strain, and add IJoz. of clean gum (Arabic), and 2f oz. of alum. In fine powders ; agitate frequently untildlssolvcd. 2 Cudbear loz., peai lash liuz., mucilage (gum Arabic), 2oz , soft water to make a pint; pour the water hot on the cudbear and pcarlash, allow the mixture tn stand for 12 hours, then strain and add i he mucilage; 1 oz of rectified spirit may also be added— Edwardlm A.

[2298,1—REMOVING OIL Paint FROM SILK. —If "Cantab" will make a strong solution ol common soda and hot water, apply hot with a brush several times over, then rinse well with cold water, he will find it answer hie purpoae.—W. W.

[221-9.]—GENERATION OF ELECTRICITY-If "Lancashire Lad" will take a piece of trou tub hoop,

about 41n. long, bend it in the form of a clamp I

and force one part between the Iron framework nnd woodwork at the end of the carriage, the other part to rest on the brasses, or, what we call, tops, you can screw It fast to the spindle box, one end to touch tbe brass, the other to touch the iron work. It has never been found to fall where properly applied. The cause of electricity is the high temper of the spindles and speed —self-acting Minder, Blackburn.

[23040-PALO DE VELA.—The Spanish word "Palo," means a wooden stnlT, a mast, and when joined to another word, tree or wood; Vahdetinte, dvewood; Palo dt Velal candle tree or candlewood; but this candlewood is not the same ss tbe candlewood of Guiana and the Autilles; this latter Is so called hecause It Is used by fishermen during the night. The "l'nlo de Vela" receives that name from its fruit, which is 3ft. long, and candle shaped; a note on that fruit has just been published, p. 45, No. 262, of our English ^mechanic, extracted, I believe, from the French review hts Mondes. Botanical name Is /wmtntitrn pcndulu*; the genus Parmentiera is au undetermined genus of Gcsneriacca, near the gonera Crescentla and Be.llonia~.The candlewood from the Antilles, Ac, comes from Amyr'u iy. (Toxtfera ?) Burseraceae. The namo ol candlewood is also given in Gulanu to the wood of Toulicea Guyancnsis, Aubl. of the soap-order or Sapindnceie; perhaps it Is also used for lighting purposes.—Bern Ar Din.

[2308.]-MORE STEAM WANTED—1 think the boiler of " D. C. W." large enough for the size of his cylinder, and if he would only be at the trouble to turn the exhaust steam Into the chimney, he would find it act as a'good steam jet, and would cause a greater draught on the flro, consequently making more steam.

-ftw. W.

T2306.1-MORE STEAM WANTED.—If " D. C. TT." pots (as he suggests) four or live tubes round the smoke flue, he will probably get steam enough, but there Is danger of superheating the steam so much as to make It act injuriously on the cylinder, packing, <fcc., so that I think tho best plan woutd be to put in a few " Field " tubes from the roof of the lire-box. They are very effective, have good circulation, and I believe that all information about 'hem can be obtained from Mr. Lewis Olrlck, 27, Lend-nhnll-strcct, London.— Q. Q- Il

[2.111.1-NEW WORM IN VICE BOX.-" A. E. B." should bore the old worm out of hi* vice box. and at the open end insert a cast steel bush, cut with a good thread to fit his screw, and fasten It with a pair of small but strong screws, let in countei sunk holes; by doing so, he will, with care and oil. Hod It better ami easier than anew box and screw.—Tangent.

[2311.]— NEW WORM FOR VICE BOX -To l.rnze the screw in a vice box, or any Inside woik. Having twisted your Inside thread round the screw, file aud fit till it reaches the bottom of the screw b-'x. taking care not to drive It lu too hard, aud make two marks, to enter it always the same way. Having driven It home, make a lute of clay and ashes, and cover the box with It (the screw part), but not much more than one-eighth thick-the reason of this is to prevent the brass running too soon, and also to protect the box— then turnout your screw nnd put lu Borne powdered borax, shaking It well about, tnen put in about 1 oz., or 1J oz., of brags bludiug wire in a fiat hank, reaehiug from top to botto.n of the box, take it in the tongs by the closed end and secure with a coupler, and having a good tire ready, put in the box, and geutly turn It rouud for the clay luie to harden, occasionally taking it out, then let nn assistant urge the lire till the box becomes of a bright cherry red, and turn it round constantly. When the wire ruus, a blue fire will come from tho mouth of the box; when you see this, uncouple the box and roll It round ou the floor, to distribute the braze, till it goes down to a low red. Having prepared your strip for the Inside screw, just enter It in tho thread of the male sjrew aud pinch both lu the vice, tapping it down into Its place with the hammer, and turning the screw rouud occasionally to nip It in a fresh place, till it is all gathered, then proceed ns above—G. E. Chick.

[231G.]-TIIE SLIDE VALVE.-The writer finds all necessary information in the " Treatise on Steam, Ac.," by Main and Brown, price 12s. ("id., used by the certificated touchers under Government, a capital work.—W. Stephenson.

[2321.] —SWAN PROCESS.— I believe that the "Autotype" Printing Company, 30, Itathbone-place, Oxford-street, London, (who possess the patent right of that process), havejust issued a manual of autotype printing, from which "Scrlbo " will probably be a'blc to obtain the information he requires.—Q. Q. R.

[2:23.]-WATER POWER.—1. .Multiply thequantlty of water per minute in li>s., by the height of fall in feet, and divide by 3'tOUO, the " nominal " h.p. The per centug^ of useful effect will, of course. dilTer according as the wheel is more or less perfect. For example: —

1 Breast wheel, (V> per ceut. Uscfuf effect! Overshot „ (15 to 70.

( Turbine, ,, 75 to 80 (with so small a

quantity of water and so smalt head, I cannot recommend turbine in " G. P.'s " case).

N.B.—As"G. P.'s" is a very elementary one, perhaps It will be necessary to Inform him that oue c. ft. of fresh water, weighs 6241b., hence, in his case, 62lbs. 4 x 20.1 c. ft. X 7ft.

= 264 horse power.

3300Hlb.

2. The volume of water behind the dam, will have no effect so long as the quantity escaping upon the wheel and the height of fall is the same. — Senex.

[2323 ]—TL'KBINK—If " G. P." can havo n dam 7ft. high, lie can work my turbine to great advantage, by having the spout fixed in the top part of the dam;

240 cubic ft. per minute will, by it, give 12 to It h.p. Pressure no object.—J. C. Shewan.

[2327.]—READY RECKONER.—The beat one published is by W.and K. Chambers, called "Commercial Tables," in whloh he will find everything he requires. —W. Stephenson.

[232S.]-DEFECTIVE GUTTER.—If " Salop" were to brush over his cast-iron gutter inside (when perfectly dry, and with the rust scraped off) with hot Dolled gas. tar or hot pitch, I think that tbe " weeping" through tho metal would be effectually stopped. - Q Q. It

[2:130]-BOOMERANG — The boomerang is a wonderful weapon, but It takes years 10 bring a man into the knack of proper use, "Et le jeune mutput la cluuulellc,"—G. E. Crick.

[i'B5.]-CONTAOT BREAKER.-E. Tucker should make (if a good amateur) or buy one of Rhumkorff 's double quicksilver contact breakers, as the only expense connected therewith is the evaporation of it small trifle of spirits of wine. He will not only find a increase the power of his coll, but fiud it a deal more manageable than the old spring and platinum point breakers. If he requires It, I will seud a small drawing and description of it, as it is an Instrument that has only come up just lately, aud I have not heard of any in England. A coil that gave formerly ouly a spark 9 centimetres long, was increased nearly B0 per cent, with a quicksilver instrument.—Tangent.

[2336.]-BRONCH IT1S.—" A Three Yeara' Sufferer" will only get rid of his affliction by change of air. Aa to Its degenerating luto consumption, there Is no fear of that, if there are no other concomitant circumstances, Bucii as hereditary or other predisposition. Ac. I cannot refrain from expressing an nplnioo tbsi it is highly undesirable to open the columns of the English Mechanic to questions of prescribing, as It off- rs the opportunity to the uninformed to perpetrate an infinite dsal of mischief by the rccommeniatloo of tt>elr nostrums. A remedy which is useful in one case, may be hurtful in nn nppnreutly similar oue.—F.R.C.S.

[2337.J-8TEAM INDICATOR.—The work recommended by the Science ana Art Department, In thcii examination, is by Maiu and Brown; Longman publisher.— W. Stephenson.

[2146.]—GEOLOGY.—The works edited by Anstcd, Jukes, nnd Haughton, are all good, and are used at the examination as text books.—W. Stephenson.

[2346.]—GEOLOGY.—" Permian" will find these two books the very best, " Introductory Text Book of Geology," Illustrated, 7th edition, 2s.; "Advanced Text Book," 4th edition, 7s. 6d. Both works by David Page, LL D , &c. Win. Blackwood and Sons, Edinburgh aud London. There Is also a "Handbook of Geological Terms," 7s. 6d., same author and publishers.—Busy Bee.

[2350.J-RAISING WATER.— The cheapest, and even best, way, la by tbe simple sucliou pump, with not less thau three clack-valves lu the suction pipe. Any plumber will put such a one lu for you.—Senex.

[2:100.]—ALUM.—The shale isslowly roasted in largo he aps, so as to oxidise tho pyrites or sulphide of iron It contalus, and generate sulphuric acid, which unites, wlt'i th3 potash iu the shale, aud also with the alumina. The shale is then placed In large pans, sunk usually in the earth, and liued with lend and fitted with steam pipes; here it Is boiled with sulphuric ncid, till aa much as possible of the alumina is dissolved. The liquor, at the proper state of concentration, is then drawn oft aud mixed with sulphate of potash, which is usually obtained direct by acting on chloride of potassium. Alum Is generated, aud being far less soluble than the sails it is derived from, precipitates in Hue grains, the liquid being well stirred dnrlng the coollug. Ihese small crystals are then washed with cold water, and then dissolved at a boiling heat, and run off into vats to cryBtalllse. A very large proportion of slum Is made with sulphateof ammonia Instead of potash, which Is obtained from gas liquor. Ammonia alum is £2 a ton less value than potash alum, but is seldom so free from Iron, and is useless for several of the purposes for which alum is employed, such aa the preparation of paper hangings, especially the white satin papers —Sigma.

[2300.]—ALUM.—The old way of extracting alum from shale, was tho following :—The "bale was first exposed to tho air, when the oxygen of the air, assisted bv moisture, effected a won erful change in it. Tho original hard slouy sub^tauco became split up luto thin leaves, and became studded over with crystals. When the alum shale thus weathered was digested in water, sulphate of alumina and sulphate of Iron were dissolved out; this solution was then treated with chloride of potassium, which decomposed the sulphate of iron, forming Bulphate of potash an* chloride of iron. Wheu this liquid was evaporated to concentration, and allowed to cool, crystals of alum became separated. The crystals thus obtained were not, however, free from iron, aid therefore -required to he re-dissolved in water, rc-ronceutraied, and recrystallUid. The same operation had to be repeated a third time before the alum wns pure. As the weathering of the shale took some years to proceed, a more expeditious method had therefore to be reBorted 10. The shale is now broken up luto frngmenw.and piled up over brushwood in lone ridges, and the brushwood being set fire to, the cualy matter of the shale begins to burn, and the whole rulge undergoes the process of roiisliug; the results of which arc the same as the weathering operatiou. Tills material is afterwards worked up as above described.—Minnehaha.

[2370.]-UNSOLVED PROBLEMS.—No saving of power would result from the use of J. Bannell's invention, however smoothly it may work, since no power Is lost through tho pre-ent mode of obtaining rotatory motion from the reciprocating piston. Many elaborate and ingenious mechiiutsius have beeu devised to obviate the use of the crank, from the most erroneous notion that tho rrauk causes a loss of power. But it will be a very difficult mat'er to fiud any moie simple or efficient contrivance for the purpose thau the crnnk, nud I would advise J. Bannell to spend neither lime nor money in further developing his invention.-W. H.N.

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