measurement, the methods of which and the men who have achieved it are beyond the limits of a letter. Perhaps "F. R. A. S." would upon some occasion enter into more particulars, which I feel persuaded would prove highly interesting to many readers. If we wish to find the distance between two or more places on the globe, we must measure by the arc of a great circle, and the number of degrees between the places will give the result. The difference of longitude is an inaccurate guide except at the equator, because although every circle contains 360°, the number of miles in each, as has been shown, considerably varies. The terrestrial globe, therefore, being the shape of the earth, even supposing there were no maps upon its surface the distance between places may ascertainedby finding their respective latitudes and longitudes and having made marks to denote them, measure the distance between the marks and proceed as above, and the thing is done.

be

T. S. H.

THE SHIPTONIAN" VELOCIPEDE. SIR,-Having for a long time carefully read the different articles respecting velocipedes in your valuable journal, and being deeply interested in the subject, I found that not one of the many varieties which have appeared were calculated, to my mind, to economise power and ensure speed. I have therefore at last decided upon and made a tricycle, as per photograph herewith, which I find answers every purpose admirably. As will be seen from it, the whole of the muscles of the body are brought into action, working as it does with both hands and feet. It is very light in construction, neat in appearance, and easy to work, and having india-rubber springs, is free from jolting. It will turn the sharpest corner with the greatest comfort, and can be steered with great nicety, There is not the slightest danger of falling, and it is safe uphill, downhill, or on level ground, as there is an excellent brake attached, by which you can quickly stop when descending the steepest hill. You can also carry a carpet-bag or box on the seat behind, and on level ground or downhill a passenger can easily be carried, and by an arrangement which I have already

ROAD LOCOMOTIVE.

B

same size as drawings; the advantages they possess are as follows:-They are made to fasten to a table or block, or better, to the box which contains them, they have a reflecting mirror, a fine screw motion for focussing, a circular diaphragm for regulating the incident light, and last, but not least, they are strong, cheap, and well-made. Fig. 1 is a front view, Bis the square body of the microscope, R the revolving diaphragm, with four different sized holes; L the eye lens, and S the back thumb-screw for focussing; the hinge at bottom is omitted in this

SIR, Enclosed I send a sketch of a road locomo-
tive suitable for two or three persons. The boiler is
2ft. in diameter, and 4ft. in height. The firebox is 20in.
in diameter, and 2ft. 8in. in height, and is
made of copper, and contains two hori-
zontal tubes. The engine consists of two
cylinders, each 4in. in diameter, and 8in.
stroke, and is two speeds action. The gear-
ing is 1 to 1 and 1 to 2, and is changed by a
friction-clutch arrangement, shown in Fig.
2. A is the engine axle, and has two cog-figure.
wheels keyed on it, one of them 74in. in
diameter, working a loose wheel of the
same diameter on the axle B. The other
is 5in. diameter, working a loose wheel 10in.
diameter, on the axle B.

On the latter axle is a sliding friction
clutch, which engages with either the wheel
C or D, and can be disengaged altogether, so
that the engine can pump water into the
boiler when standing. On one side of each
loose wheel are small projections, with
which the friction-clutch engages, and the
gear can be changed whilst the engine is in
motion, or whilst standing, independent of
any position the engine may be in. The
front wheels are each fixed in a forked
shaft, and connected by means of a rock
shaft to a spring-catch lever, by which the
engine is steered. The water is con-
tained in a small cistern under the car-
riage, and the coal is placed in front of
the driver. The engine works up to 150lb.
pressure.

This form of steam carriage may not be in accordance with the ideas of every one, yet, taking all things into consideration, I do not see how it can be much improved upon, and in design I have put the steam carriage through more than twenty different metamorphoses.

WILLIAM STANLEY, Eyre-street, Chesterfield.

planned (and but for sickness would have carried out),
I could make it for two to work without increasing
the weight of the machine more than 10 or 15lb., by
which means I should obtain double power, and make
it to travel at a much greater speed with two persons
on it than with one. The levers could, nevertheless, be
put on or taken off in a few minutes, so that either one
or two could ride. The woodwork is French polished,
and the iron painted black, and then varnished. Its
speed is such that although I have run with several
PERRY'S MICROSCOPE.
two-wheelers (and among them were some very skilful
SIR,-Enclosed I beg to hand you sketch of my new
riders), I have never seen the person who could keep microscopes, which will no doubt meet the approval of
up with, much less pass, me. Several gentlemen have
advised me to secure it by patent, but I prefer giving
my brother readers the benefit of it, if they think it of
service.

ERNEST R. SHIPTON, Vine Cottage, Knowle, near Bridgwater.

ALGEBRA.-A QUIET CHALLENGE. SIR,-I am glad to have "C. H. W. B." agreeing with me that many of the most pretentious algebraic problems of the day are worthless. Let me remind C. H. W. B." that even Colenso (Alg. 8vo., p. 390) stigmatises a search after just such "impossible" roots in the Equation Papers of St. John's College, Cambridge, 18 "useless and profitless." Still, "C. H. W. B." maintains that "algebra is extremely useful." I admit, the notation is useful; but, Euclid observed the very principle long before algebra began. In Euclid, A is an angle, B is a triangle, Ĉ is a square, or any square, and E F, F G is a rectangle, though only two sides of it are thus given. This is all the good there is in zy z. Arithmetic has as much; for instance, in "Walkingbame's Tutor's Assistant," by Young, interest is i, and p is principal, r is rate, t is time, a is amount; so the formulæ is conveniently given as prt + p = a." This is not algebra, though it may look algebraic. The real essence of" Algebra " is in its equations; here, if anywhere, the "science" is distinctive. Let, then, "C. H. W. B." adduce some common-sense question; let it be intrinsically some serviceable affair; let it be fairly and fully stated, and plainly worked out, intelligible to the "meanest capacity." with answer and all; let its drift be to exemplify how algebra is the best or the only method. And then I will engage to prove, that the algebraism is no advantage; and that the point can be discovered, easier and better when the whole science of algebra has been utterly discarded.

many readers of the ENGLISH MECHANIC. GIMEL. microscopes are made from square

Fig. 2 is a section-M is the inclined mirror resting on a block of hard wood t; the light, after passing through the diaphragm hole, is reflected upwards in the direction of the eye lens (dotted), causing the object under examination to be well illuminated; the light is regulated by using a larger or smaller hole of diaphragm, as the case may require. The top of the microscope has a dove-tailed groove for receiving a strip of glass xx. Pis the slide carrying the lens; this slide, after passing down the groove G, terminates in a screw, y, which, passing through the thumb-piece S, gives the motion for focussing. His the hinge for fixing the box; the microscope can, however, be held between the thumb and finger, if so preferred.

The power of this little instrument may be roughly estimated at from 20,000 to 30,000. The heart and blood of a flea are distinctly seen in motion; a few human hairs resemble a bundle of faggots, and hundreds of lively beings are seen in a small drop of water. Cheese-mites appear like horned beetles, and a flea resembles a young lobster! E. PERRY.

WATER ANALYSIS, &c. SIR,-In your impression of the 13th a correspondent signing himself " W. R." asks for my opinion as to the relative capabilities of Wanklyn's and Frankland's processes for the estimation of organic matter in water. I am sorry he has required my opinion on the subject. I must decline depreciating either, as there is no doubt they are both very good for general purposes, in their way, the preference being generally given to the simplest, and that which is easiest of execution. This process of estimation (Wanklyn's)

R

These which has been used with such good results by Angus brass tubes Smith never:heless has its defects; the other process

give another reason. We can always tell by the form
of the body whether a mas has much muscle; we can-
not see the muscle because of the skin, but we judge
by the outward form and development, which always
corresponds. The same kind of reasoning will apply
to any other portion of the body, such as the stomach,
bowels, lungs, &c. If any of these are small or large,
that part of the body where they are located is either
enlarged, contracted, and diminished. I consider my
own head to be an overwhelming proof of the truth of
phrenology. The extremes are so great, large and
small, and so various, that if a million heads were exa-
mined I don't think one would be found like it, and
yet it exactly corresponds with my peculiarities in
every respect, including both intellectual, moral, and
animal faculties. Now, taking into consideration that
the similitude is is so exact and complete, I say
most seriously that it is more than a million to one
against such being the case if there be no truth in
phrenology.

(Frankland's) also has serious defects, the greatest of
which is in the supposition that all nitrates and
nitrites are formed by oxidation of nitrogenous animal
principles; Boussingault's experiments, to my fancy,
prove the contrary.
With all the estimations around us of organic
nitrogen, carbon, nitrates and ammonia, it is very little
the public in general understand. They want water
analysed at as low a figure as possible, and the
analyst generally reverts to "chameleon' as the
most ready, and one which with ordinary manipula-
tion gives good results.
As regards the relative proportion of organic carbon to
the nitrogen present in waters," W. R." has instanced
3. 1st, 2 to 1; 2nd, 5 to 1; 3rd, 10 to 1. Now, although
there seems no proportion existing between them,
there really is, though in an indirect way. The third
sample of water would probably be the purest, which
may be proved by examining the reports of analysis;
thus, above Reading the proportion is nearly 10 to 1,
and the nitrates stand at 0, but it must not always be
AN INVENTOR AND SELF-TAUGHT MECHANIC.
inferred that the impurity may be measured by the
proportion of organic nitrogen present, taken as re-
[Our correspondent considers his "own head an over-
gards the organic carbon, for, in one instance, a pro-whelming proof of the truth of phrenology." We dare
portion of 3 to 1 was obtained, yet the water was
venture to affirm that if he were introduced into a
purer than that which contained 11 to 1. I think the room of, say half a dozen men, including a poet, an en-
best method for practical purposes is to express the gineer, a statesman, a botanist, a preacher, and a mer-
amount of organic matters by the number of grains chant, he would not be able to distinguish one
per gallon of oxygen necessary for its complete com-
the other by their heads; neither do we believe the
bustion.
cleverest phrenologist living would be enabled to dis-
I am not aware that it has been tried to convert the tinguish them if he were permitted to manipulate their
quantity of organic nitrogen and carbon into grains bumps in the dark. This may be an experiment worth
per gallon. If it has been, and an approximate result trying.-ED. E.M.]
gained only, why it is best to use permanganate at
once. One part of nitrogen might correspond to many
different weights of organic residue, and the same
may be said of the organic carbon.

Now with regard to W. R.'s" four queries:Frankland's process may, I should think, be applied to sewage water, but after evaporating to a small bulk the fluid should be finished at a very low heat, or preferably in vacuo, to avoid loss of volatile constituents. 2nd. There is no doubt that ammonia in ammoniacal salts may be estimated by the Nessler test, but, to my fancy, normal acid is preferable. Same answer as above. Question 4th. That quantity of organic matter which requires one equivalent of oxygen for complete combustion, measured by the number of 10cbe. of a chameleon solution containing 0159 grms. per litre, required to produce the perma

nent tint.

3rd.

GEORGE E. DAVIS.

STRENGTH OF CHAINS.

SIR,-I see Mr. Tolhausen, Jun., hails from Manchester; he may, therefore, inform me upon the follow ing:-I have read his article on "The Tenacity of Chains and Ropes." Will he be good enough to say if the formulæ he gives are practically carried out? From all I know they are not, for chains are required and do actually work with heavier loads than his rules estimate. For instance, the Lancashire and Yorkshire Railway Company at Manchester have chains to lift 10 tons, but according to his rules it should be over Their other chains have a working load in proportion. From what I can see, the proof strains in his Table II. are more agreeable to the actual weights chains work at on cranes. Anent his remarks in same article of the difference existing between the strength of studded and short link chains, I do not think the proportion is 7 to 9. I know from actual tests made at our works that a short link chain has broken a studded chain of equal diameter of link, and although the Board of Trade provide in their tables of proof for a stud chain to bear more than short link, they say nothing of the breaking strain or ultimate strength. You see, after a certain weight is on chains, the iron begins to stretch-i.e., the link becomes longer but narrower, and having got to a certain point the stad between does not suffer it to go farther, but as strain is still applied and link extended in point of length, it separates, generally top and bottom, or at AA in Mr. Tolhausen's sketch of link. In short link or unstudded chains, however, the oval link, by being stretched, becomes straight sided having nothing to stop it, so that the strain is not applying itself to one portion only. When these links go it is generally at the hinder part, or at the W. A. E. W.

neck of the shut.

COLOUR BLINDNESS.-PHRENOLOGY.

COTTON SPINNING.

from

SIR, Your querist, Edward Habergham, p. 104, No.
269, asks for information about the backing off (not
baking off) motion of a mule frame, and also about
the working of the cam shaft. Perhaps he will not be
mation (which would take up too much space to give
offended if instead of giving him the required infor-
clearly), I give him a little advice which is also season-
able for other correspondents. The sum total can be
written in a few words," Think for yourself." When
a person gets into the habit of asking other persons'
assistance as soon as the least obstacle presents itself,
without trying to surmount it, he has a great tendency
to place no reliance at all on his own ideas, but to float
along with the stream, and at length probably finds
himself in the whirlpool of complete ignorance which,
by-the-bye, is not altogether bliss-Charles Rabache
to wit. For my own part I would not place entire
dependence on a statement made by even such a
genius as our harmonious brother the "Blacksmith,"
except his ideas would agree with my own, or else by
careful study I could come to the conclusion I was
wrong. Of course I don't mean to say that every
man's reasoning powers are equal-by no means-or
that a Rabache will balance a Proctor if weighed in
the scales of Science, but I do mean to say that it
behoves all who intend to progress either in cotton
spinning or any other study to think deeply and
earnestly for themselves, and learn to depend on their
own discretion and judgment. When they cannot
arrive at a firm decision, or there is any doubt on the
subject which they cannot themselves remove, then is
the time to fall back on the advice of other persons.
They should bear in mind that there will not always be
"Harmonious Blacksmiths," Sigmas," and "Adepts,"
to refer to when they are "fast." My advice to
E. H. is to go and stand behind the headstock of
his mule, and mark, learn, and inwardly digest" all
its different movements, and be determined to find
what he requires, and I'll guarantee if he has any
brains at all (no offence) he will know more in an hour
than I could write in five.-I mean as regards the
principle on which it works. But if my prediction
does not happen to "come true." and he gets stuck
in the mud, which no doubt he will before he gets a
practical knowledge of it, then I shall be most happy
to help him out and render him any assistance he may
require.

I hope these remarks will be received in the same
spirit as that in which they are written.
THE HARMONIOUS COTTON SPINNER.

quently you can make a better sample of flour
with silk than with wire. In the second place, a silk
bolter, if properly constructed, does not take more
than one-fifth of the power that is required to drive a
wire machine that will do a fair amount of work. In
the third place, there is a great saving effected by
using silk instead of wire, as a silk clothing for a reel,
if it is constructed right, and the silk put on properly,
will last from five to eight years at an average, accord-
ing to the quality of silk; for instance, the Swiss silk
will generally out wear the French, whilst every
miller will know the trouble and expense generally
attending a wire machine, for if they are overfed, or a
piece of iron gets in them, there is a stoppage of the
machine, and a sheet of wire, or perhaps several, to
put in. But with a properly constructed silk, nothing
of the sort can happen. There are other advantages,
but I am afraid I am trespassing upon your space. In
my next, if you think it will be of interest generally to
millers, I will point out some disadvantages of the
present silk bolters, and suggest means by which they
may be obviated, as there does not seem to be the
slightest doubt that ultimately, for dressing flour, siik
must supersede every thing else at present in use.
E. DAVIES, 92, Spring-street, Edgbaston, Birmingham.

ON THE "LEAD" OF THE "SLIDE VALVE" IN
STEAM ENGINES.-ANSWER TO "STEAM
SPIRIT."

SIR, The "travel" of the slide valve, the amount of its lap," and the extent of its "lead," are the three essential elements of that most important part of the steam engine, and these three elements, or proportions are so inseparably connected, so completely dependent on each other, that they cannot be considered separately or independently; and to speak of or attempt to discuss the effects of any one of the three upon the distribution of the steam to the cylinder, without at is nonsense, and cannot possibly convey any practical the same time taking the other two into consideration, or useful idea on the subject.

A quarter of an inch of "lead" for a given engine, may be too much, or it may be too little, or it may be neither, and no engineer (unless he knows nothing of the subject) can undertake to say which it is, without knowing at the same time, the "travel" of the valve and the amount of its "lap." What is the object, the use, and this history of the lead of the slide valve? In the early days of the steam engine, the slide valve was lead, as it frequently was, the piston would arrive at made with but little or no lap, and when set without the end of its stroke before the exhaust port comone end of the cylinder, and the admission of steam menced opening for the escape of the steam from of the return stroke. Indeed, owing to the wear and to the other end, preparatory to the commencement slackness of the joints of the connections between the eccentric and the valve, it was often late in the performance of its daty, and in many an old engine the piston often made two or three inches of its stroke before the change took place at all; it was then found that an improvement in the working of the engine resulted from giving the valve some lead; by-and-bye a little lap was added by some genius, bolder and further improvement was found to result, inasmuch as more speculative than his neighbours, and a still sive action, to a trilling extent, as the small lap and a collateral advantage followed in the shape of expanlead combined, caused the steam to be cut off a little before the termination of the stroke.

without lap (except in special cases, which I shall not From that time out, no more valves were made notice at present, as I am now discussing the common simple slide valve in general use), and new valves, with more or less lap, were put into many old engines, whose valve chests were long enough to accommodate longer valves with longer strokes, but, in general, the improvement, and hundreds of these antiquated valve chests were not long enough to admit of the machines have struggled on to the present day without improvement, and not susceptible of any, and, in all human probability, will see most of us laid under the "sod," who now smile at their antiquated proportions, their grotesque appearance, and their insatiable appetite for fuel and water.

It will be seen from the above, that the lead was a SIR,-In reply to your correspondent," Harmonious very important thing with valves which had little or Cotton Spinner," page 204, respecting the benefit to be no lap, and short travel, and the proper amount of it derived from the flyer of a roving frame leading, and vice versa, he says, that with the bobbin leading, no was the subject of many a warm dispute amongst the waste will be made, which is perfectly true, but his have old millwrights (the engineers of former days), and I latter statement, that they cannot be run at as great a myself been sometimes specially privileged, when only a very young apprentice, by being perSIR.-I was much surprised to read the articles on speed, is at variance with my experience se far, for mitted to be present at some of their Saturday night colour blindness inserted in the MECHANIC. I always having had the management of three frames with the and Saint Monday discussions, and of course I thought thought that phrenology fully accounted for such bobbin leading, and one of the other construction, we the disputants were wonderfully clever fellows, and phenomena. To suppose that defects in the formation ran the three at a greater speed than the one with flyer my great ambition was, in future years, to become of the eye is the cause, is about the same as malfor-leading, although it was going as fast as the machine such a "shining light" as "big Martin Murphy," or mation in the construetion of the ear would be in relawould stand. Possibly, with other makes of frames, "Red Jack Carter," or " Old Dick Mead," or "Bob tion to music. I know a person who is so defective the results might vary considerably; this I am inclined Thomas" (all these luminaries have disappeared in his perception of music that he cannot tell one to think is one main cause. With respect to the size below the horizon years ago, and have gone to that tune from another-every tune to him is about the same; for cop bottoms, I have used, and found the following place where the "wicked cease from troubling, and and why should it not be so in regard to colour? Be- starch, and 2oz. sweet soap; put these in a bucket, I changed my mind, as the conviction forced itself mixture to suit best in our case-namely, 1lb. best the weary are at rest." R.I.P.), but in after years, sides, some people have great difficulty in recollecting and fill three parts with water, then turn a small jet upon me, that all which these eminent authorities" and distinguishing forms and shapes, sizes and distances of objects, localities, &c. But we never think of steam into it until it boils; should the mixture advanced, could not be "gospel," inasmuch as no two of attributing such defects to the eye. I should like get too sad as it boils, add a little more hot water amongst them could agree on that (or any other) subto know why an exception is made in regard to colour. until you get the proper consistency. This composi-ject, notwithstanding the amount of whiskey they Some people don't believe in phrenology. Now, if tion was liked best by us, and I have no doubt will drank, and the quantity of chalk they used in drawing they would take the trouble to examine it and try to suit elsewhere if carefully tried. Any further aid I diagrams upon the tables, and walls, and floors of the understand it, I think they would. I feel as certain of can give, I shall be happy to do so. its truth as I do of my own existence. If I am asked JOSEPH B. CROSSLEY. publichouses, and the incredible amount of profound balderdash they talked in explanation of them, and for reasons for being so confident, I will give a few. finally, the quantity of "skin and hair" they made fly If I look at an object such as a chair or table, I know from each other when weaker arguments failed or that they are such by the form and dimension of each. were exhausted, the whiskey all drank, the money all It is simply observation combined with reflection. spent, and the chalk all used up. Now I do the same by the head. I find that the form of the head corresponds with any peculiarity which the person to whom it belongs possesses, whether intellectual, moral, or animal. I find that those who are fond of constructing, inventing, making various things have one particular part of the skull prominently developed, while those who have no such inelination have the same part depressed. If the heads of all those who read the MECHANIC were examined, I believe that the lump of constructiveness would be fo und fully developed in most of them. I will now

TO MILLERS.

SIR-I presume from "J. S.'s" inquiry, on page
182, that he wants to know the advantages of dressing With valves of modern make, and whose lap is con-
flour through silk, over dressing it with a wire siderable, say one-fourth or one-fifth of their travel.
machine. As I have had great experience in the the amount of the lead is not so important, and the
manufacture and erection of both, I will state a few difference between an eighth inch, and a quarter inch,
of the advantages of the former method. In the first and three eighths inch of lead in their effects upon
place, in a silk bolter there is, if I may so term it, no the distribution of the steam, is very inconsiderable
artificial means used to force the flour through the indeed. "Steam Spirit (query 2532, No. 265) asks me
silk, but it is done simply by the revolving of the reel;"why I would give so much lead (in.) to the engine
whereas in a wire machine, it is forced through by the in question ("Relwot's" engine; see my letter on page
brushes, by which means there are quantities of small 39, No. 262). He says," he should have thought a quarter
greys forced through the wire with the flour; conse- inch of lead decidedly too much for any stationary

"distribution" by a further reduction of the same
valve's travel to 3in., and Fig. 3 illustrates its perform-
ance under this condition. A single glance at the dia-
gram shows that the influence of the lead is vastly
increased, and that its power of altering the time of
the occurrence of the several events is very great, as
is plainly shown by the wide-spread positions of the
lines representing the crank at the times of their
occurence.
"Pre-admission," in Fig. 3, occurs under the in.
lead, when the crank is at P, and is yet 25° from the
horizontal line, and the piston is a full inch from the
termination of its stroke. Under the in. lead the
crank is at P# 1510 from the horizontal, and the piston
is full in. from the end of its stroke, and under the
fin. lead the crank is at P70, the versine has vanished,
and the piston has ceased to move when pre-admission
occurs.

The "cut off" occurs under the fin. lead, when the crank is at C, and the piston has made 6in. of its stroke. Under the in. lead, the crank is at C", and the piston has made 8in. of its stroke; and with the in. lead, cut off occurs when the crank is at C', and the piston has made 10in. The exhaust occurs with the in. lead when the crank is at E", and the piston has made 14in. of its stroke. With the in. lead the crank is at E, and the piston at 15 in.; and with the in. lead the crank is at E, and the piston at 16 in. of its stroke when that event occurs.

EMIGRATION-TO" COTTON CLERK." your request, both as regards Canada and Australia. Can SIR,-I will at the earliest possible moment'attend to you not during the interval acquire some knowledge of farming? You will find that the information required to ensure prosperity is not intuitive, bat must be learnt. R.G.S.

THE SOLAR SPECTRUM.

SIR, I gather from a perusal of your interesting paper of the 20th inst., that some of your readers are in doubt as to the dark lines of the solar spectrum being really due to absorption in the solar atmosphere. Permit me to remark that a final proof of this lies in the fact that when a vividly incandescent prominence is seen on the aun by the method I proposed in 1866, some of the dark lines change from dark to bright.

Mr. Proctor, who writes (page 211) that an increase in the density of our own atmosphere would not increase the breadth of the atmospheric lines (that is the dark line produced by the absorption of our own atmosphere) has doubtless overlooked the results of the experiments carried on by Dr. Frankland and my self, in which we show that increase of density does increase the breadth both of bright and dark spectral J. NORMAN LOCKYER, 4, Victoria-road, Finchley-rd., London, N. W.

lines.

THE SOPER RIFLE.-MATHEMATICS. SIR,-In the account of the Soper rifle, I should have stated that it is fixed by means of two screws, not one, as mentioned.

"T. J. O'C." wishes for some information upon

algebra; if he will kindly have patience the reward will follow. We mathematicians can scarcely claim

more of your space than we do now. This may be seen
by the fact that your waste paper basket con-
tains no small quantity of paper spoiled by being
covered with "letters" and figures. How do I know
this? Why some of my longest lucubrations have
been found therein, helped downwards by a shorter if
not better solution. It is really a difficult matter to
cater for so many and diverse minds, and I for one
give you great credit for the discrimination used, and
the excellent results obtained.

Would" Bernardin," and R. A. Proctor, Esq., kindly
favour me with their private addresses through our
Editor?
C. H. W. B.

[We certainly do not insert all the mathematical matter sent us, and for the following reasons. It would occupy too much space, and it is difficult and expensive matter for the compositors to compose from manuscript copy. When the slightest mistake occurs in the formulæ very frequently all the calculations are thereby vitiated. We have, however, too much respect for" C. H. W. B." to give the waste basket many of his contributions, and particularly what he contributes on other matters under another name.ED. E.M.]

VELOCIPEDES-THE

"PHANTOM" WHEEL.

be that I am not yet used to the "style" of Mr. Henry SIR, It may be mere stupidity on my part, or it may W. Reveley's English, but for the life of me I cannot

make out the drift of his letter on page 131.

If I rightly understand what he says about the "Phantom" wheel, I must tell Mr. Reveley, with the greatest deference, that he altogether misunderstands us. We have never "proposed" thin plates for rubber tires. We actually make and use half-round rubber tires, which we are prepared to match for speed, safety, ease of work, and lasting qualities, with anything he can bring against them in the way of velocipede wheels. He tells us that the tires of what I suppose I may call the velocipede of the future "must not be tired in the way we propose. Well, in spite

are

of this dictum, we are satisfied with what we doing and have done with our rubber-tired wheels for

several months past.

A word, too, as to the "velocipede of the future." Would it not be a real mercy to the general reader, and a grateful boon to practical velocipedists as well to confine mere proposals and schemes such as this of a "light carriage for 30 miles an hour with a slow treadle movement," and all the tall talk about them to occasional special numbers? We shall never be tired of your admirable articles and illustrations of machines which have been actually made and driven, even where they have only gone a very short distance. But let us have done with railways to the moon.

papers

ness of the chief nebulæ visible to a Sin. achromatic,
so as to get an idea of what I am to expect, when look-
ing for the fainter ones.

Omicron" stated that the light of D'Arrest's comet
was to be 0.126. What does that mean? I beg to
second the resolution proposed by J. Brown, p. 228,
in regard to an index for " Notes and Queries "; as
it is much wanted and ought, I think, to have been
done before. I hope it will be carried unanimously.

H. W. BISHOP.
MESSRS. CUNNINGHAM AND M'CARTHY'S
IMPROVEMENTS IN MOTIVE POWER.
SIR,-The invention described in your last number
(page 223) in a most extraordinary one, especially as
put forth by gentlemen evidently possessed of great
knowledge in the practical details of machinery. The
application of spiral springs as a motive is a very old
device, which cannot be usefully employed except in
the case of watch and clock machinery, or such like,
and for this reason, that the power required to wind
up such spiral springs is greater than that required to
do the actual work proposed to be accomplished,
owing to imperfect elasticity, friction, and other
obstacles.

But Messrs. Cunningham and M'Carthy are not con-
tent with these so-called improvements in motive
power, their aim is apparently perpetual motion. For
by having two separate spiral springs, they propose
that while one is uncoiling and driving the carriage;
it shall at the same time cause the other to be wound
up by means of its winding wheel touching the road,
so as to be ready to act when the first shall be
Nothing more or less than perpetual motion.

exhausted.

HENRY W. REVELEY, Reading.

astronomers as

"HOW TO KEEP THE CLOCK RIGHT," &c.
SIR, I am sorry to see that "Luke the Labourer',
P62) gives such an unfavourable notice of the book.
How to Keep the Clock Right," especially as it con-
taius testimonials from such
Sir
J. F. W. Herschel and the Rev. J. Challis, M. A., F.R.S.
The former distinguished astronomer says that "so
far as he can perceive, the method seems to be a very
good way of keeping exact time, and very little
costly, as well as attended with hardly more trouble
than would be required for merely uncasing the tele-
scope and looking through it." The Rev. J. Challis
says, "he considers the method to be good in principle,
and to be very practicable." I have not yet tried the
method, but intend to do so; and I confidently expect
to get the time within a sec. by observations of three
or four stars. I think Luke the Labourer may
overcome his difficulty if he constructs a chart of the
350 stars in the zone to be observed, carefully denoting
the star magnitudes by black discs of variable diame-
ters: 8th magnitude stars should be represented by
dots only just visible. The catalogue numbers should
kind-scale 8in. 10.
be placed near each dot. I have made a chart of this
I can readily distinguish the
mapped stars from others when directing a telescope
to the zone on a clear night. On a cloudy night I
would recommend "Luke to observe several sup-
posed catalogue stars, and then to argue from his
observations to the catalogue by comparing the time
intervals, rather than argue from the clock to a star.
I humbly endorse the opinions of the great astro-
nomers above mentioned with regard to this method
of keeping the clock right

Will "F.R.A.S." or Mr. Proctor kindly answer the following questions?

1st. What is considered to be the best method of

determining longitude by astronomical observations?

2nd. Are all or most of the visible occultations of

stars, of which data are given in the "Nautical
Almanac," observed at Greenwich or other public

observatories?

THE ELLIPTICITY OF THE EARTH. SIR,-That Mr. Beardsley should have failed in the difficult task proposed to himself has probably surprised no one who has devoted himself to the study of astronomy; and however satisfied he may be with his own reasoning, I may venture to say that he has convinced none of your numerous readers; and further, I think I can also say that the reasoning of your correspondents will have failed to convince him.

The answering arguments that Mr. Beardsley's letters have drawn forth, while they have been, perhaps, as good as his reasoning has deserved, have been weak. I believe one gentleman asserted that the fact of a person's travelling continuously in a certain direction, and arriving at the point from which he started, was a proof of the sphericity of the world; another, that if the earth were flat, it would be possible to fall over the edge. It is the use of such weak arguments as these, and which are easily confuted, that give rise to the doubts in the minds of some of the truth of the generally asserted figure of the earth. Neither am I satisfied with the course Mr. Beardsley in his letters something new, and not have been has pursued. I had hoped that we should have seen treated to a repetition of the childish arguments that we are so familiar with. In fact, I had trusted to been disappointed. Perhaps the fault was mine; for have seen something original in his letters, but have I had without sufficient reason concluded that as Mr. Beardsley was not a follower of Newton and Laplace, he was necessarily the inventor of a system himself. It seems to me now that Mr. Beardsley is in the fortunate position of being able to throw stones at other people's glass houses, without erecting one of his own for other people to throw at.

But supposing that Mr. Beardsley limited himself to the wide field of overthrowing the existing theories, there is still much left for him to do; for he has yet to consider those facts with which astronomers more particularly concern themselves, from which the figure of the earth can be deduced without measurement of its surface, and with which geodetical instruments have nothing to do.

I had hoped to have seen the disciple of the school of "Parallax treat of the theory of precession and nutation, and to have seen him overthrow the reasoning of astronomers that deduce from the magnitude of these quantities, taken in conjunction with the density of the earth, the amount of its ellipticity. Nor did I think that the observed inequalities of the moon's motion would have been forgotten and left unexplained; and I am led to think that it is just possible that Mr. Beardsley was unaware that astronomers are able to discover the form of the earth by other means than measurement of arcs of meridian and pendulum experiments.

collected the figures that express the ellipticity of the
It may be interesting to some of your readers to see
The general
earth deduced from different methods.
agreement between them is such as to confirm, were
confirmation needed, the expressed opinion of philo-
sophers that the form of the earth does not differ
greatly from an ellipsoid of revolution. Airy's discus-
sion of what he considered the most accurately mea-
sured arcs of meridian gave e = 0·003352.

Bessel, from eleven arcs of meridian, some the same and some different from those selected by Mr. Airy, and discussed by a totally different method, deduced e0003356.

The ellipticity deduced by the Astronomer Royal from the consideration of the pendulum experiments equals 0.003471.

Should Mr. Beardsley be prepared to battle with the more intricate problems of astronomy, the results of which I have mentioned here, I will venture to beg space for him, although, I must confess, it is only for 0. the gratification of my curiosity.

The phenomena of precession and nutation give for a result e = 0.003323; and finally, the discussion of the inequalities of the moon's motion, in longitude 370. latitude, give respectively e = 0.003387 and e = 0003370. A slight discrepancy is noticeable in these figures, but so slight that our surprise is elicited, and our admiration excited, that modern measures and mathe3rd. Can I obtain the observed times of disappear-matical analyses have been carried to such a point of ance and reappearance of certain stars as seen at an perfection as to make even these small discrepancies observatory whose longitude is known; so that by a matter of controversy and speculation. comparing these times with the observed times at any station the error of the lunar tables might be eliminated and the difference of longitude found by the method given in Loomis's " Astronomy?" of the moon on the meridian made at an observatory I should like to know the result of any observation for the purpose of detecting errors of the lunar tables; also what is the most probable value of the earth's polar semi-diameter, the equatorial semi-diameter being considered as unity? I have only lately noticed that some corrections are required in the formula for ing longitude from observed eclipses and occultations, given in the Apperdices to the "Nautical Almanacs for 1836 and 1837. These formulæ were prepared when Buckhardt's Tables of the Moon were used; but since they are now replaced by Hansen's Tables the constant log. of- =943537 requires correction.

I remember being very much struck at hearing Mr. Glaisher, the eminent aërenaut and astronomer, express at a meeting of scientific men an ironical desire that the Society should be favoured with a series of "On Failures," for he felt, he said, that a great deal more good could be accomplished if' gentle-computing eclipses and occultations, and for determinmen would be frank enough to come forward and confess wherein and how their experiments had been resultless than by the continued iteration of new theories and speculations as to what might be done. Now may it not be so in regard to velocipedes? How many of your readers may have stopped short on the threshold of great improvements, which may be reached after all with a little help from the experience of some one else! Try and induce some of your correspodents to go in for this part of the subject. It will be a healthy change, and may help to keep others upon solid ground. If Mr. Reveley could only be induced to put together his 30 miles an hour light carriage with slow walking motion, and all the rest of it, what a nice chapter he might be able to write for your new heading!

COLOURS OF STARS, &c. SIR,-Will some of our astronomical readers inform me which is the proper time to see the correct colours of the stars? Our "F.R.A.S.," Mr. Proctor, and Mr. Webb call Sirius a pure white star. Now I do not think I am colour-blind, but, to me, it appears at night (which I should call the proper time to see the stars), a pure green with dashes of red; several friends agree with me; and in Lockyer's " Elementary Lessons" it is classed as a green star. In twilight it appears white, but not so as the night advances. Will Mr. Proctor *** F.R.A.S." kindly give me the comparative bright

log.

8

P

I find that for the present ephemeris of the moon, = 943606; and this constant must be used instead of the former in the formule. This log. appears on pp. 130, 134, 175, 183, and is used in determining here the ogs 0.56394 and 2.99236 must be used instead of the legs. 056463 and 2-99167 On p. 134 the nat, number 2725 must be replaced by 2729. Of course these alterations are well known to practised computors; they may not, however, have been noticed by some fellow amateurs.

R.A. AND DECLINATION OF STARS, &c.
SIR,-"Scorpio" asks for a book containing the above. May
I be allowed to recommend Mr. Proctor's Handbook of the
Stars," containing the correct places of 1500 stars from 1 to
5 magnitude, and also a very easy way for laying down the
meridians, &c. It is a 5s. book, but very useful. I wish to
thank "Amateur," page 236, for description of pancratic tube.
Although I did not do it right at first, I succeeded with a
small tourist glass, and was greatly surprised at the continual
increase of power. Could "Amateur" give the reason?
H. W. BISHOP.

Aqua can prepare standard solutions on many bases, as Mohr's, Griffin's, Sutton's, British Pharmacopœia, &c. The best mode is to use as a standard normal solution one of a single equivalent in grammes dissolved in one litre of pure water, and for a decinormal standard a tenth of an equivalent per litre. Then, of course, every cubic centimetre used indicates an equivalent in milligrammes of the eubstance being estimated. As, for instance, to take a very simple ease of estimating nitrate of silver, a normal solution will contain 58:5 grammes per litre of sodic chloride. Suppose we find it requires 20 cubic centimetres of this solution to precipitate the silver as chloride from the nitrate this then indicates 20 equivalents in milligrammes of nitrate of silver, or 20 times 170 milligrammes of the river salt-that is to say, 34 grammes. If "Aqua" wishes for practical details, he can have them; and reference to your number for May 27th, letter, "Water Analyses," will show him an answer to his query about permanganate of potass. "A Sister Reader" will find it quite impracticable to dissolve plumbago. URBAN.

THE EYE-INVERTED PICTURES. SIR, It is an established fact, and well known, that all objects presented before our eyes project an inverted

3. Aërostatics. the rest or equilibrium of aëriform
bodies under the influence of forces.
When motion is the result of the application of forces
to these conditions of matter, we have the following
subjects:-
1. Dynamics-the motion of solid bodies produced
by the influence of forces.

2. Hydrodynamics-the motion of fluid bodies pro-
duced by the influence of forces.

The percussion turbine, exhibited by Mr. Kelly, C.E., the invention of Mr. Cheetham, of. Manchester, is quite a centre of attraction. Its great beauty is its simplicity-nothing to break, and nothing to wear except the axle. I have no doubt it will be heard more of.

picture upon the retina, but the picture, when transmitted to our mind, seems to us upright. The question has therefore been often repeated, does our mind, in reality, receive an inverted or an upright image? Without investigating any of the explanations with which we meet in books on optics, allow me to give The Pneumatic Loom of Mouland and Coulong is ene fact, which may throw a new light upon this particularly worth notice: it does away with picking Question:-I once knew an intelligent little boy, then about, or nearly, five years of age. His eyes seemed levers, bowles, peckers, straps, and all these trouble2. Aerodynamics, or Pneumatics -- The motion of some affairs, and works so smoothly and noiselessly to be in perfect order, yet at candlelight, in certain that 100 of them in a shop would not make as much noise positions, when an observer was in the line of the aëriform bodies produced by the influence of forces. reflected ray the left eye was crystalline; there was I think the above arrangement is much superior, as an ordinary sewing machine. A pair of vertical enno black colouring matter in the interior, no optic both as regards simplicity and comprehensiveness, gines combined by Messrs. Coates, occupy a prominent Mr. McCreery nerve-in fact, observations proved the boy to be blind than that given by the Rev. E. Kernan, becanse each position; they seem to work well. In the left eye. Although blind on one side, the boy signification is clearly defined, whereas in his arrange-exhibits his celebrated spinning wheel, so many of which he has made for the Royal Family and the amused himself by drawing simple objects, such as ment none of the terms statics, dynamics, &c., are exhorses, dogs, fowls, and houses, very correctly, upon plained at all. I see he has added a new division nobility. It is presided over by a merry old lady, paper and slate, but all these drawings were inverted relative to the vibration of bodies, and which he consi- who, with nimble fingers and ready repartee, delights an admiring audience, one of whom made the remark (upside down) The boy was often told that his draw-ders might be entitled palmatics. Well, I will not "Is it any ings were upside down, but he smiled and said " They dispute with him as to this division, as it makes very that the wheel worked very quickly. are perfectly right." No doubt he saw all objects in little matter whether it be considered as a separate wonder" she says; "listen to the fine music she has." Why? what effect has that upon her?" is askedthat position. The bright little fellow soon proved that division or not. "Just THOMAS J. O'CONNOR. says the old woman, ""she's (the wheel) like his lett eye was an exception, was a fearful malady; all other jennies" it puts her clean mad. it inflamed, and fungus developed itself out of the cavity. After about ten months' suffering the boy passed away. While he was ill, in hours free from pain, he still followed his amusement, drawing inverted animals upon slate, which again proved that with one eye, and one optic nerve inverted, impres

sions were transmitted to his mind.

I may here observe that the above case is different from any case where an eye may be lost by accident. In the latter case the optic nerve is seldom-its rudiWith the boy ments, however, are never-destroyed. the very rudiments of the optic nerve on the left side were wanting; in its place were the rudiments of the fungus. Taking all the circumstances in consideration, I can only come to one conclusion-that with a pair of normal eyes the image presents itself to our mind in an upright position. The single eye presented inverted images; double combinations produce upright pictures. It seems in normal eyes to be this:The inverted pictures on the retina are travelling along the optic nerves; the latter, as we know, interlace each other. Here an interchange of impressions must take place. In this very act the pictures are reversed, and, resolved into one upright picture, presented to our mind.

THE WELSH SHEPHERD.

THE MOTIONS OF THE MOON AND EARTH. SIR,-For years past there has been a great deal of quibbling about the proper term to use to express the motion of the moon in relation to the earth. This motion (not taking into consideration external disturbances) is precisely what it would be if the moon formed part of an immense globe, having the earth for a centre and reaching beyond the orbit of the moon, the period of rotation on its axis being equivalent to a lunar month. Allowing for the accelerated rotation of the earth, it would seem that the earth and the moon might be portions of the same solid globe, and yet retain the same relative motions and distances that they have at present, and that the moon revolves round the earth under precisely the same conditions as any portion of the circumference of a globe revolves round the centre of the same.

F. W. M.

SCIENCE FOR THE YOUNG. SIR,-Will you allow me to draw the Rev. E. Kernan's attention to a few errors which he has committed in his treatise on "Science for the Young." Under the head of law third, he says, "Time is required to overcome the inertia of a body whether at rest or in motion. When force is applied to a body, a certain amount of time is necessary for the production of the effect of motion or rest.' In this statement he has committed a serious error by confounding the term inertia with a body in motion as well as at rest. Inertia has nothing whatever to with a body in motion any more than momentum has to do with a body at rest. Let us ask ourselves, what is inertia? and what is momentum? The answers to these questions are extremely easy. The quality which enables a body to resist the sudden communication of motion is termed its inertia, and the quality which enables a body to resist the sudden extinction of motion is termed its momentum. Therefore, he should have written law third, as he calls it, thus :-"Time is required to overcome the inertia of a body at rest, or the momentum of a body in motion. When force is applied to a body, a certain interval of time is necessary to produce the effect of motion or rest in tha body. Where does he intend to insert the law of reaction, which is an axiom of statics, that is, a selfevident truth, or one which admits of no other proof than universal experience, and which tells us that action and reaction are equal and contrary, that is to say, A cannot act mechanically upon B without A itself being reacted upon equally, but in an opposite direction, or, in other words, that whatever force one rigid body exerts upon another rigid body, the latter opposes that force by an equal force, which is called its reaction. This law is of as much importance as any other in statics.

TO TRISECT AN ACUTE ANGLE.
SIR,-Draw a straight line K B H. From the point
H draw the 3 angles B HD, DHC, and CHA equal
to each ether. From any point B draw the 3 angles
Through
H B D, D B C, C B A each equal to B H A.

THE MIDLAND AND WESTERN DISTRICTS OF
IRELAND

SIR,-Will you kindly allow me the space in the
ENGLISH MECHANIC, to ask a question or two, which
I shall feel obliged if some of our courteous geological
friends will answer. Travelling through the Midland
and Western districts of Ireland, I passed over
immense deposits of limestone, some specimens of
which were literally crowded with fossil remains,
which I believe are called Encrinites. I wish to know
whether they are animal or vegetable relics, and
whether they existed in the sea or in fresh water.
They occur in great abundance near Athlone, in
Connemara, and Joyce's country. The deposit assumes
a different appearance, that of a mottled grey marble,
well suited for building purposes. Other rocks in the
vicinity of Ballanahinch gave unmistakeable evidence
of I think a good per centage of copper, perhaps not
sufficient to pay for the working. I should like the
opinion of one who has visited the same locality, and
better versed in mineralogy than myself. I was much
surprised to hear that this beautiful part was but
seldom visited by tourists, a fact I can only account
for that its beauties are so little known. To the angler
it offers rare attractions; the Loughs Ina and
Glendalough are well stocked with salmon and trout,
and are situated within an easy distance of the half-
way house (usually called Lynch's Hotel), and the
Recess Hotel, both of which are passed by the mail
cars en route from Galway to Clitden. To the
antiquarian special interest would be attached
to the old abbeys of the neighbourhood, the old
abbey of Cong being the resting place of the last
Irish King. Part of the cloisters have been restored,
and the whole ruins are kept in repair by Sir Arthur
Guinness, whose hall they almost join. The bones and
fragments of monumental effigies so plentifully scat-
tered about these old places awaken deep interest and
speculations as to the lives and characters of those
races long gone before. To the lover of natural
beauty and quiet solemnity, I would say, visit
Kylemore Pass, the group of mountains called the
Twelve Pins, ascend the one called Mul Rhea, and
he will gain as fine a view of mountain scenery as
can be viewed in Ireland. The Sun setting behind
the mountains skirting Killery Bay, which in the
autumu are covered with the heather bloom, gilds
the whole scene with surpassing splendour. But I
must close. If any brother reader would wish to visit
these scenes and many others in the Western High-
lands, and will correspond with me, I shall be most
happy to give him any information as to the route,
and other incidental matters.

F. HARWOOD, 33, Newark-street, Leicester.

Again, at p. 79, he arranges the divisions of mechanical philosophy in the following manner - viz., statics of solids or statics, statics of liquids, hydroBELFAST WORKMEN'S EXHIBITION. statics, statics of gases, pneumatics, dynamics of solids or dynamics, dynamics of liquids, hydrodyna- SIR, I herewith send a detailed account in three mies, dynamics of gases, pneumatics, palmatics copies of the Belfast News Letter of the Workmen's (acoustics) of solids, liquids, gases. Now, I must tell Exhibition now open in Belfast. The exhibition is Mr. Kernan that he could not have written them in a very well worth a visit, and many hours could be promore inexplicable manner, and he has not alone fitably spent there in examining the various ingenious written them in this inept manner but he has placed products of the working man's brain. This item the statics of gases and the dynamics of gases under from a provincial town of Ireland augurs well the same signification-namely, pneumatics, which is for the success of the main exhibition to be Two or three turmost absurd, and not to be met with in any standard shortly opened in London. work on the subject. The above divisions of me- bine wheels are here at work; in fact, the motive chanical philosophy when properly written should power of the machinery section is given by a turbine be arranged as follows-viz., inade by the eminent engineers, Messrs. McAdam Bros. Soho Foundry, Belfast; they have long been successful makers of these water engines, having devoted particular attention to their manufacture for some years past.

1. Statics-the rest or equilibrium of solid bodies under the influence of forces.

2. Hydrostatics-the rest or equilibrium of fluid bodies under the influence of lorces.

66

A revolving shutter for shop windows or bookcases is well worthy of attention, and will no doubt come into notice. The imitation bronze statues of Holland are very handsome. VIVIS SPERANDUM.

on

TRADE AND COMMERCE. SIR,-Your correspondent "Herbert," writes these important subjects with a pithiness which is almost convincing. He states that the balance of imports over exports represents the profit of a nation, and illustrates it by an imaginary ship, which, sailing with £18,000 worth of goods, returns laden with £29,000 worth. Here is something for the consideration of our ministers and merchants. Let the Government at once prohibit exportation-all that we import will then be clear profit. Let our merchants send forth their ships empty; the merchandise with which they return will then be so much to the good. But, unfortunately, there is a little flaw in the argument. Your correspondent's assumption would be perfectly correct, if the trade were carried on by barter only, but this is not the case; we might cease to export, and yet, for a time, continue to import as much as ever.

The subject of trading with foreign countries is one of vital importance to the working man, and is not to be settled by a rash conclusion, or even by asking, as one of our Cabinet Ministers did, "Why should we refuse to buy cheaply from foreign countries, because they refuse to buy cheaply from us?" The answer to this is, that by doing so we pay the wages of the foreign workmen, who make these cheap goods, and therefore there is just so much the less for our own workmen. When the amount becomes considerable, as it is at the present time, our men are compelled to emigrate in large numbers. It is pretty plain that for each foreign workman we support in this manner. one English workman is compelled to leave his country, or to become a pauper.

The whole subject is too vast and too important to admit of proper discussion in the limited space you can devote to it. My only object in writing, is to point out what I believe to be an error in your correspondent's reasoning, and to caution your readers that a subject which offers so many points for consideration, cannot be settled by pithy sentences or specious questions.

F. W. M.

DEW CAPS FOR REFLECTORS AND μ2 BOOTIS'

SIR, In answer to "Hugo," I must say, that in the cool winter evenings, and indeed on most nights when a deposit of dew occurs on the tube, and when the telescope has been an hour and more in use, he will find a dew cap imperative. My tube has an aperture of 11in., and I find a cap extending to 1ft. beyond the prism, is generally required on dewy nights, although many nights (as at the present time), do occur when the prism may be exposed for a long time. Inside, and at the upper end of my cap, I have placed a ledge, for the lodgement of a series of tin stops, which vary the aperture from 10 to 7in. Before I used a dew cap, I frequently had to remove the prism, warm and dry it before the fire, replace and readjust it. all this took up too much time. In using even a 4in. refractor, I find a cap 8in. long absolutely necessary.

For the information of "H. A. C.," during the present season, I have found 2 Boötis well divided with 10in. of aperture, and achromatic power of 300, the same with 9in., but with sin. and same power, the discs were in contact; with Huyghenian eye-piece, of about 350, the discs were split. At the same time, I found a of Cancri well divided, with apertures down to 9in. and the same powers, but could not split it with any power of 8 inches, mainly owing, I suppose, to the components of a Cancri being of greater magnitude than those of 2 Bootis, although their distance is somewhat greater.

M. W. B. COULCHER. Downham Market.

BOOMERANG.

SIR,-If "Vivis Sperandum" got a piece of wood, say ash or beech, 2in. square and 2ft. long, and steamed the middle of it well in a box, he could bend it to the shape of outline of boomerang, and leave it till cold and hard, nailed with a few cleats to a flat board; then rip it lengthwise into five thicknesses of each, or less, and the grain of all would be the right way to resist Boomerangs used to be sold at the London fracture. toy-shops larger than his dimensions, and with ends Those we see in the about square with each other. museums are frequently scarcely bent at all, and only a foot long, or a little more. Is his name "Vivis" or "Vivus? J. K. P.

DARK LINES IN THE SOLAR SPECTRUM. SiR,-I think Kirchhoff was quite right in his preferring what his spectroscope plainly taught him to