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The height being 1ft., the velocity through his pipe
will be 8ft. per second; therefore when the pipe is 9in.
in diameter, area being 63-6in., the discharge per
second will be 6107-25 cubic inches.-STREBOR.
[1859.]-MATCH MAKING.-Mr. Ch. Mertens,
at Lessines (Belgium), patented three months ago in
that country, his lately invented dipping machine for
match making.-RAIMOND STAES.

When

[1865.]-WHITE METAL BEARINGS. the chair is cast, have it hollowed so that it will hold the metal, fasten the chair in its place, put in the spindle packed up, put some clay round the spindle to keep the metal from running out, pour to the centre of spindle, cut off any projecting metal, lay some strips of cardboard on each side of the spindle, put on the top part of chair clay round the spindle as before, and pour through oil hole. This mode requires neither fitting nor boring. I have seen lead used alone, and wear very well.-MILLY. [1887.]-PUTTY.-Let "Hortus get about 201b. of whiting, and, pound it up fine, then add enough raw linseed oil to make it into a stiff uniform dough. I found it took three pints, and that was not quite enough. Then hammer it well out, as thin as it will go, and work it well till it comes soft enough. I was told that one pint of oil was sufficient for 151b. whiting, but found three pints hardly enough. This is the best and cheapest putty. He had better add the oil as he wants it not all at once, and warm the putty before

a fire.-AUGUSTUS.

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[MARCH 25, 1870,

£6 10s. per mile for putting up.-MILLY.
rails; 18. 6d. per 100 for sharpening stakes; and
[1935.]-EQUATION.-

(2)

bx + cy + a z = c z + ay + b z = a2 + b2 + c2 (2), (3)
≈ + y + z = a + b + c
From (2).. (b c) x + (c a) y + (a - b) z = o.... (4)
From (1) and (2) .... (b c) x + (a c) z = a2 + - c
(a + b) ..
(5)
a) y = b (a + 4-

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From (4) and (5), (a
+ b)

From (4) and (6), (c
+ c).

a great profit. A hole is made in the shells, and
they are strung on threads of palm fibre; 40 shells = 1
string, Many merchants in Lagos occupy eight
cowries weigh 80 or 90lb., the white Indian ones 35 to From (7) and (8) by transposing and dividing,
or ten girls stringing cowries. 2000 blue African
40lb.; 2000 about a dollar,-BERNARDIN.

a-c

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a2 + be a2 + c2

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c (a + b) - (b − c) z whence, by multiplying up and reducing, b (a + c) (a - b) = (a2 + b2 + c2 − a b − b c − c a) = a3 + b3 — c3 – 2 a2 whence, dividing each side by the co-efficient of s, it + 2 ac2 - 2 b2 c + 2 b c2 - a b c will be found that z = a + b - c. I should be glad to see a neater solution from some abler pen than mine. -SENIOR OP.

[1896.]-EQUATION.-in the last number of your
paper, page 640, C. H. W. Biggs announces his inten-
tion in a short time to commence" his "Notes on
Algebra." Permit me to express a hope that "C. H.
W. Biggs will first master the question before under-z
taking to teach others, otherwise those readers of the
"Notes," will be in danger of falling into errors, as,
ENGLISH MECHANIC who put their trust in his
for example, that the square of -
- 10; or that
√5x + 10 is -5x

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in several foundries in Glasgow; it is better than
The following is what I have seen used with success
beeswax:-When the pattern comes from the finishing
[1970]-VARNISH FOR IRON PATTERNS. -
shop smear it all over with oil rubbed
on with a bit
of waste, put it in the drying stove all night, so as the
repeat the dose. I can recommend this, having seen
oil will burn in; if not in a hurry for the pattern
it done and having done it myself pretty often.-N. L.
[1978]-LIQUID GLUE-I have made a strong
strong acetic acid; add a small quantity to the
powdered glue, cork tight, and let it stand for some
common recipe for ordinary liquid glue, and which I
hours; you will find it soften; by adding more acid
have used, consists of 8oz. best glue, dissolve in ipt.
you can make it of the consistency you require it. A
CHERRY.
water, add 24oz. nitric acid; cork up tight.-J.

lowing, I think he will find one or both answer his
[1981]-ENAMEL.-If Mr. Walker will try the fol-
purpose:-No. 1. Oxide of tin 6, flint 3, borax 1. No.
2. Oxide of zinc 2, Cornish stone 8, whiting 1.-IOTA.

Wood's Algebra, he will find in the chapter upon Quad1896.]-EQUATION.-If Mr. Biggs will consult ratic Equation, page 118, the equation fully discussed in its unaltered form: x + √5x+10=8.-H. C. C. stone into twelve oil stones when I was an apprentice, [1910]-TURKEY STONE.-I cut a lump of turkey partly with a sheet of copper, and partly with a sheet of lead, of course fitted to wood frame for convenience, in both cases with sand and water, but I cannot [1889.]-BELGIAN AND FRENCH PERIODIremember which cut it quickest.-JACK PLANE. CALS.-No journal similar to our ENGLISH ME[1913.]-GAS BURNERS to burn common coal gas CHANIC is published in Belgium or France. In no are not of much use to illuminate dissolving view apone, such variety of instructive matter is to be found. paratus. I have tried several, including a 50-hole aras they respectively and for the most relate to some/gand, but always found camphorated colza oil more liquid glue by treating Russian glue with a little special branch of science. If my fellow correspondent effective. My experience led me to adopt the improved Argente" will communicate with me through our oxyhydrogen burner when I want more light than oil MECHANIC what subject he more especially prefers, or will give; the apparatus is very simple and quite safe. what branch of science, mechanics, or technology, he wishes to be informed on, I shall be glad if I can to [1929]-LACQUERING.-In answer to "Inquirer," answer his demand.-RAIMOND STAES beg to send him the following method for lacquering [1894.]-CHINA GRASS DIVISA.-I have also brass-work. If he is going to proceed on old work he been puzzled by tha: name, and never could get any must first boil the articles in strong soda and water, conclusive information about the plant; the follow-so as to get off the dirt and old lacquer; then scrub ing article appeared in several French reviews:them with sand and rinse them. The next process is "Dr. Grothe, director of the manufacture of Ram- the dipping, for which he will require an earthenware melsberg, near Berlin, employs with great success, for pan capable of holding the articles, which he must fill making figured stuffs, much in demand for England, 2 pails of clean water and a box of sawdust. If he with aqua fortis, which he can obtain at any chemist's; yarn of China grass, white or dyed in different has any means of keeping the sawdust hot all the colours. He produces the China grass divisa (sic) in a plantation he planted, and which yields 50 per cent. better, and a nice clean brush. Now he will have to dry fibre, and 30 per cent. long and very fine filaments. proceed as follows:-Tie the articles on copper wire, In the mountainous regions where the soil and the dip them in the acid, then rinse in the water and well tion of flag, the Urticaceae in general, and the China that want relieving this must be done with a bright severe temperature form a serious obstacle to cultiva- then brush the sawdust off. If there are any parts rub them in the sawdust till thoroughly dry, and grass in particular, resist perfectly. (?) The Prussian Mining Office has taken into serious consideration a articles are ready for lacquering ; but if the articles steel burnisher and a drop of stale beer, then the culture which seems to fui nish an accessory and very precious resource to the miners of the Harz and of have tarnished, to restore their brightness he must dip them again, but he must dilute the acid with ten Now for lacquering them he wl want something to beat them on; a plate of iron with a gas-burner under little strain. The heaviest parts of the engine are transmitted to the crank very equally and with very it will do; but if he has an oven that will do as well. brought very low down in the boat. The disadvanlacquer with it; he must heat the articles so that he -H. CHAPMAN. to get French gold lacquer and mix a drop of red heavy, very costly, and not applicable to screw boats. camel-hair brush lay the lacquer lightly on, care being counting the number of steps in walking, not me for can just bear the hand on them, and then with a soft taken not to lay it on too thick or to get the articles use now. Time tells the distance travelled over, for too hot. If there is anything else that Inquirer" the walking rate is nearly uniform for each individual, [1987.]-WHAT IS IT?-It is a pedometer for wants to know, I shall be happy to inform him.- and is soon ascertained by counting a few mile stones W. SEABROOK. once or twice.-H. W. REVELEY, Reading.

Hanover."

(1985.]-SIDE LEVER ENGINE.-I beg to inform "Suffold Amateur" that the side lever engine was purposes. I think it was invented by James Watt, but that which used to be almost entirely used for marine I do not know if he patented it. The principle of this nected with the piston by means of a cross head are down at the sides (of the engine,) and they had and engine is similar to a beam engine, only the beams are levers is connected with the crank. The advantage of connecting rods. The other end of the beams or side this kind of engine is that all the moving parts are balanced by each other. The connecting rod from

I made several inquiries, but always times its weight of water, rinse and dry as before, the beam to the crank is very long, therefore motion is

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posed also that divisa might be a fault of impression If he wants that red gold tint on his articles, it is best tages are that it occupies a very large space, it is very

for dioica, or for diversa, different kind.-BERNARDIN.
[1895.]-COWRIE COINS.-The following letter
from Lord Alfred Churchill, to the Secretary of State
for the Colonies, which I extract from the Technolo-
gist, of July, 1865, deals with this subject:-"The
Council of the African Aid Society have had under
their consideration the recessity and advantage of
finding some metallic substitute for the cowries,
hitherto in use among the natives. A currency ought
to be adapted to all the wants and habits of the people "R. W. M.," that the ironstone of this district con-
[1931]-LINCOLNSHIRE IRON.-I beg to inform
for whose use it is intended. Cowries, as a circulating
medium, have been for a long time in use in the tains in its raw state from 30 to 35 per cent. of iron of
countries of the Bight of Benin and the Niger territo- a very good quality. The average price for the ore in
ries. Since the aunexation of Lagos to the British waggons at the mines is from 4s. 9d. to 5s. 3d. per ton,
crown, all the English coins have been introduced and 58. 3d. to 58. 9d. per ton delivered at the nearest
there. They are coming into use among the natives, wharf. Should " R. W. M." require further informa
but do not suffice for the general wants of that portion tion, I shall be glad to help him.-BLAST FURNACE
of the community. The lowest English coin in circu- ENGINEER, Frodingham.
lation is the farthing. The value of this is 30 cowries,
but a great many articles of daily consumption are
purchased much below that price. Unless, therefore,
some smaller coin be introduced, cowries cannot be
abolished or replaced as a circulating medium. In the
interests of progress and civilization, of which Lagos
is an outpost, it is desirable that the currency should
be solely metallic. The Council of the African Aid
Society have had an opportunity of seeing the small

Chambers' "Tables of Logarithms," contains seven
[1934.] LOGARITHMS. -
- To "Y. P. W."-
figure tables of logs., log. sines, cosines, &c., and natural
sines and cos:nes, with a heap of other information;
proper title "Mathematical Tables," gives a few
examples at commencement to explain the tables, has
no treatise. Can be had anywhere for 38.-MATY.
[1954]-CEMENT FOR PARAFFIN LAMP.-Let
drop of water, to keep the shellac from burning. When
get twopennyworth of shellac, and melt
melted he then may fill the brass socket and stick in
his reservoir; he will find he has a good job.-LING

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worn in the waistcoat or other pocket, and measures
[1987]-WHAT IS IT?-I believe the instrument
the distance walked. Each step taken causing a vibra-
"Querist" has got hold of is a pedometer, which is
tion of the weight, which acts in one of the toothed
wheels.-IOTA,

would stamp the books in gold for a very small charge
[1989.]-NUMBERING BOOKS. A bookbinder
or the numbers might be painted on the backs in oil
colours, black figures on a white ground.-IOTA.

but blot immediately with blotting paper; a few hours
[1989.]-NUMBERING BOOKS.-Gum the back of
alter size with common size or glue water, let this
your paper, write your title numbers, &c., in good ink,
thoroughly dry, and then varnish with pale Course
up, and stick on in the ordinary manner. Of course
we suppose a sheet or a few sheets to be done at the
same time to be worth this amount of trouble, but

complete work on this subject is that by Dr. Percy. It [1990.]-METALLURGY.-The most recent and is published by J. Murray, price 218.-BETA.

coins one mil each-now being struck at Her Ma- it by the fire in a tin cup, to which he may add a small when done this may be termed everlasting.-S. T. jesty's mint in London, for Hong Kong Those coins being each one-twentieth of a penny, or one-fifth of a farthing, would be the value of six cowries. thing worthy of mention can be bought for a lower sum FISH. As nothan six cowries, those coins would respond to all the minor wants of the native Africans, while their being [1964.]-CARPENTERS' PRICES.-I have put up perforated, so as to enable them to be strung as cow-fencing of four railings and one stake post: have morries are now strung, would render them equally safe tised the post and pointed the railings for 6d. per and convenient as cowries, while they would not be length, but they were 10ft. long, that however is immore than one-seventh of the average weight of the material. The posts and rails had to be put up, but if smallest cowries used in the interior trade. The Coun- put up at per chain it would make a considerable difcil of the African Aid Society beg leave, therefore, to suggest to Her Majesty's Government that it would gratis.- UNLEARNED PLATELAYER. ference; they were laid out on the work ready for use be advisable, and of general advantage, to introduce perforated coins of a similar size and value, in the 100 for mortising; 1d. per pane of 4 rails for chopping keel and fixing stem and stern-post, let“ S. F.” make [1964,]-CARPENTERS' PRICES.-Posts, 12s. per [1991.]-CANVAS CANOE.-After laying down the

[1991] CANVAS CANOE. - I would persuade ribs; it is impossible to obtain good lines, or in less our friend against making his canoe of canvas on technical words, no curve can be obtained; the outline boat would consist of straight lines as nearly approaching the curves necessary as is posible in lessening the distance of the point of attachment to the frame, but the result is in the highest degree unsatisfactory.-S. T.

t

14

[2005.]-RAZOR PASTE.-Crocus and tallow, mixed
with pestle and mortar. Obtain at a watchmaker's
tool warehouse.-S. T.
[3005.] RAZOR PASTE.-In reply to "Dundreary"
I can safely recommend the following:-Reduce emery
to an impalpable powder, and sift through fine gauze
to catch any large particle; mix the powder with as
much spermaceti ointment as will form a thick paste,
and lay on the strap.-GITCHE MANITO.

[2005.]-PASTE FOR RAZOR STROPS is thus
made:-Oxide of tin, levigated 1oz., saturated solution
of oxalic acid sufficient to form a paste. This compo-
sition is to be rubbed over the strop, and when dry a
little water may be added. Oxalic acid having a great
affinity for iron, a little friction with the above pow-
der will give a fine edge to any razor.-TAUTAU.

Be or more templets to be placed across the keel at berals. These templets represent transvere sections af the boat at their several positions, and to them are ad temporarily the slips forming the skin or outer picking. These run longitudinally from stem to , and may be wide and 1" apart. "S. F." will ed this the best plan, as without the slips the canvas apt to bag between the ribs. The ribs or timbers are steamed to make them pliable by placing them in a wooden box connected by a tube with a common pot covered with a close lid, or they may be boiled in water till soft. They must be put in hot, and nailed in position at once, or they will stiffen. They can be nailed on the keel with common copper nails, which I should advise in preference to iron. There should be a rim or gunwale round the boat, as it strengthens her considerably. I have used canvas myself for a covering, but find it retards the boat by its friction, and believe good strong duck would be preferable." After nailing on, give it three or four coats of white lead. 6ft. is too short for a canoe; 10 or 12ft. is little enou h, with about 2ft. 6in. beam.-STEERSMAN. (1995.1-DEFECTIVE PIANOFORTE.-Let a good joiner let in a piece of hard wood a suitable width where the crack exists, screwing some good screws with a sharp deep worm in the joint itself, the worm or thread of which will hold sufficiently tight to prevent the piece inserted from drawing up by the tensio of the wires.-S. T.

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the weights of the arms, which weights we may con-
sider as applied at their middle point: we have for
the equation of equilibrium-

P x 2a + Rx a = Q x 2a + S x a
Hence-

(P

And

(SR)
(PQ), but I believe

Q) × 2a = (S-R) x a PQ = The querist says (S R) = this is an error of copy.-FRANCK. [2000]-PROBLEM.-Y. R W." should state that the difference is double, not half of the difference between P and Q.-J. K. P.

[2000.]-PROBLEM-Is there not some mistake in the statement of the problem given by "Y. R. W." in the ENGLISH MECHANIC, March 11? I find that the difference between the weights of the arms equals twice the difference between P and Q, and not (as we are asked to show half the difference between P and Q. I find an expression for the difference between the weights of the arms in terms of P+Q in the following manner:-Let L F and FM be the 2 arms of a lever

P

M

IM, and FM be the heavier by reason of extra matter uniformly distributed over its whole length FM. The weight of this matter will evidently act at G, its centre of gravity, and the distance FG will be equal to FM. Denoting the difference between the weights of the arms by B, we have, by the equality of moments:

-FM.Q+

FM.B

2

= FL.P FM.P, Since by hypothesis FL FM

2 FM.Q+ FM.B = 2 FM.P FM.62 FM.P - 2 FM.Q Dividing each side by FM, we have B =2 (P-Q) or difference between the weights of the arms equals wice the difference between P+Q. "Y. R. W." is welcome to this solution, and I hope he will find it satisfactory. I wish for the ENGLISH MECHANIC that the new volume may meet with the success which has attended its predecessor-W.B., Leeds. [900]-PROBLEM.-Let length of each equal arm The weight of each arm (being uniform) may be considered as acting wholly at the centre of gravity, and we from the fulcrum. Call weight of 1's army,

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PNEUMA. [2005.)-RAZOR PASTE.-No. 1. Prepared putty powder loz., powdered oxalic acid oz., powdered gum arabic 20grs., mix with water. brown paper, collect the ashes, reduce to a fine powder No. 2. Burn some by rubbing it in the fingers, rub on the strop, or mix with No. 1, instead of the putty powder. Tried and band good. The second is my own invention, and is very cheap.-AB-OTH-YATE.

[2006.] TO CLEAN STEEL ORNAMENTS.
Young Wife" may clean them by rubbing them over
with some fine emery and oil to get off the rust, and
then removing all the traces of oil and emery, rub them
with a clean brush with some crocus and water; lastly,
polish off with a little dry crocus-this will clean them
if they are not very rusty; but if they are it will be
impossible to do anything with them.-A. A. A.
[2007.)-TEMPERING DRILLS.-Heat your drill
Oa dull red, allow it to cool slowly, then rub the
int for an inch or two up the neck clean and bright,
ither on a brick or wet grindstone; now lay the point
f your drill on a lump of iron previously heated red
h, and the moment your drill has attained the colour
you require, dip and stir it in cold water (or oil, if a
small tool). The gradations of temper are-mild,
blue, hard, dark straw, very hard, pale straw.-S. T.

[2007.]-TEMPERING DRILLS.- Heat the drill
1in. up from the point until it becomes blood-red;
then dip it in water about an inch, hold it to the light,
and you will see a blue tint, which gradually descends,
and when it is about 1-16th of the point slack it.-
WILLFREW.

[2008]-CONTENTS OF IRON PANS. - To find
the cubic contents of iron pans with circular or rather
spherical bottoms, you must ealculate the body of the
pan and the bottom distinctly. The body of the pan
is a cylinder; to measure it multiply the square of the
diameter by 7854, and the product will be the area of
the base; multiply the area of the base by the height,
and the product will be the solidity. If the bottom is
half of a sphere, multiply the cube of the diameter by
5236 and divide by 2; the quotient will be the solidity.
If the bottom is the segment of a sphere, to 3 times
the square of the radius of the base of the segment
add the square of its height; multiply the sum by the
height and the product by 5236 for the solidity; add
the solidity of the cylinder to that of the bottom for
the total contents. If the
measurements are taken and
by 277-274 (cubic inches in 1
calculated in inches, divide
gall.); the quotient will be the
multiply by 64 (cubic galls. in
contents in galls. If in feet,
1ft. nearly), the product will
be also galls. Example-

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do. in gals..
4974-2
-MILES JENNINGS.
[2008]-WHEEL CUTTING.-In answer to "Burs-
lem," special machinery seems indispensable for a
special job, and it is absurd to rig up an apparatus for
a few wheels when you can get them cut for you for a
tride. What you must have for the purpose is a divi-
sion plate, containing all the numbers you want, and
a cutter frame to carry the cutter, on a vertical spin-
dle. I have seen patterns cut, or rather planed out
of white metal in a lathe by means of a single point
tool of proper form held horizontally.-J. K. P.
which the tubes are fixed into multitubular boilers, in
[2012-MULTITUBULAR BOILER. The way in
as follows:-They are put loosely in first, and whilst
in their place a conical plug of steel is driven into the
ends so as to open them a little, and so fasten them
into the tube plates. If they are not perfectly water-
tight they have to be caulked a little to make them so,

-H. CHAPMAN.

[2021. MAGIC LANTERN. In answer to "George,"
I would say he will get as much practical information
on the construction of magic lanterns in the back
numbers of the ENGLISH MECHANIC (Vol. VI., pages
395, 424, 444, &c., &c.) as any work on the subject that
I know of. As to plate photograph lens being
suitable for a magic lantern, I know by experience
that there is no lens more so if a long range is
required with a 4in. condenser. The lantern requires
to be 45ft. distant
cover an 18ft. screen, and will /
give a clear and distinct
picture with oxy-hydrogen
light. A-plate lens will
give the same size picture
at about 28ft. distant. Con-
densers for magic lanterns

various forms. No.

to

3

plano-convex and double convex, No. 3 two plano-
plano-convex, No.

is 54in

It?" by a "Mere Phantom," 1s., is a capital book on the lantern.-C. WARD.

[2016.]-COTTON WASTE.-The cotton waste is first sorted, and all hard lumps, rope ends, scrap iron, &c., thrown aside; it must then undergo the following processes:-1st, bowking with lime for 8 to 10 hours 2nd, washing in dash wheels 15 to 20 minutes; 3rd, scouring 6 to 8 hours; 4th, sweetening; 5th, bowking with soda ash 6 to 8 hours; 6th, drying. The bowking

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is done in kiers of wood or iron heated by steam. The 1st requires about 4 to 6cwt. of lime made into thick cream, and freely sprinkled amongst the waste as it is thrown in the kier. The washing requires plenty of water, and is done in ordinary dash wheels. After being washed the waste is steeped in a solution of muriatic acid in water (2 to 3 per cent. of acid), then drained and sweetened by placing under a shower bath, using plenty of clean water. The 2nd bowking is done with soda ash, and takes from 3 to 5cwt. of ash per ton of waste. The drying is generally commenced in an hydro-extractor, and then finished in a stove or the open air, which is preferable. If "NO" desires further information I shall be happy to give it to him.-FEU FOLLET.

[2022.]-VENEERING.-Soak your glue until it gelatinises in cold water, carefully boil in proper gluepot, warm your veneer; all the rest depends on three points of detail- cleanliness, close contact of the surfaces, and the expression of all excess of the glue -i. e as small a quantity really between the surfaces o be united as is practicable.-8. T.

tin foil; when it has lost its quickness apply with [2023.]-AMALGAM.-Kill some mercury with pure small quantity only of clean tallow.-S. T.

[2023.]-AMALGAM.-Mix your amalgam with as much lard as will make a thick paste and spread it on the cushions with a knife.-GITCHE MANITO. following useful:-Melt together 2oz. of tin, 2oz. of mix with 4oz. of lard, and ioz of bees-wax. BETA. zinc, and 6oz. of mercury; when cold, powder and

[2023.]-AMALGAM.-"T. O'Connor" will find the

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J. Land mean an india-rubber ball?-if so, we can [2024.] MENDING GUTTA PERCHA.- Does tell him how to repair it. A gutta percha ball seems to present no difficulty. A patch could be heated and

put on, unless, indeed, the ball be very old; then the material will be found perished, and very difficult to deal with.-S. T.

[2029.]-PHYSIOGNOMY.-Lavater is the best authority. There are cheap and dear editions of his work.-BRIEFLESS BARRISTER.

[2035.]-STAMPING IN COLOURS.-Presses for this work may be bought by any one, and with prac tice any may do it. A prepared gummy ink is spread is then wiped clean with the ball of the thumb, leavon a steel die in which the device is sunk; the surface ing the ink in the device. The paper to be stamped is placed on the die and a leather matrix" is brought down on to it by means of the press, and is by it forced into the cuts, the ink adhering to the paper forms a coloured impression in relief. This process is called "relief "stamping.-IOTA.

[2038.]-SUN DIAL.-" T. S. H." to " Jupiter.". The hour angles for a horizontal sun-dial in latitude eastward and westward, are 12° 20′, 25° 15', 89° 14′, 51° 2540, beginning at the 12 o'clock line, and reckoning

convex, which I think gives the best results, No. 1
being only used for the common construction of
lanterns. Distance between condenser and front lens
Condensing lenses may be had mounted
almost from any optician. The price of a 44in. is £2 28.;
3 in., 18s.-J. E. V., Edinburgh.
condensers 33in. brass cells is from 148. to 158. Any
[2021.]-MAGIC LANTERN-The price of double
hill, or Pumphrys, of Birmingham, may be relied on
optician will supply them, but Cox, of 26 Ludgate-
for quality and price. I have seen a 4-plate portrait
lens used with good effect, but "Guernsey" writes
from personal experience, therefore with authority on
the subject. "The Magic Lantern, and How to Use

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make up his weekly report, and send to the architect, draw most of the working drawings, and measure up all extra work; in fact, he is nothing more than the superintendent of the work in the absence of the architect.-DELTA.

(2043.)-FILLS.-" Wry Face" finds it a difficult matter to take pills in the ordinary way. Nothing is better than an oyster; it is a capital thing to carry a pill to the stomach Use it in this way:-Slit the thick part of a native oyster and put in the pill, then swallow the whole. Children who are fond of oysters, and who cannot be made to swallow pil s, may be thus effectually deceived. Another mode of taking offensive pills, or nauseous medicines, is to prepare the mouth beforehand by seme aromatic substance; for instance, chew a clove or a piece of orange peel or lemon peel, or in lieu of this first put into the mouth a bit of alum.-TAUTAU.

Some

[2043]-PILLS.-In reply to "Wry Face," there are several plans for rendering pills tasteless. of these plans are patented, some not. The principle aimed at in all is to cover the pill with a film which shall resist the action of the saliva during the short time that the pill is in the mouth, but that shall be removed in the stomach. metal, as gold or silver leaf, or a varnish composed of This film may be either balsam of tolu, or some similar substance dissolved

is mistaken in supposing that it is merely water in the
[2057.]-ZINO PLANT.-"A Late Subscriber, E. S,"
bottles in which zinc trees are made. It is a solution
of acetate (sugar) of lead, in water that is used for
the cork of the bottle long enough to reach to the bot-
that purpose. A piece of copper wire is attached to
tom, and if you want branches to your tree put pieces
of wire across, you finally fasten a small lump of zinc
on to the top part of the wire. take care that it is im-
mersed in the solution, cork up your bottle, and in a
few days your tree will be complete.-HENRY CHAP-
MAN.
rium manufacture consists in having a rabbet for the
[2059.]-AQUARIUM.-The great bugbear in aqua-
glass instead of a groove, the former entailing trouble
and vexation without end. Take, then, a groove, and
make the putty of red lead and copal varnish; in a
must be used as made, as it sets very quickly.-S. T.
few days all is hard, sound, and insoluble The putty
fish of many kinds in my aquarium for years: it is put
[2059.]-CEMENT FOR AQUARIUM.-I have kept
together with red lead putty, common putty is useless.
with white lead (in oil) as stiff as it can be conveni-
Red lead putty is red lead (in powder) worked up well
PLANE.
ently used; leave it a few days to harden.-JACK

[MARCH 25, 1870.

little bit of nit. silv. to replenish waste from kaolin.
I shake it well, and then filter, afterwards adding a
and filter. I have sometimes, especially after using
above entirely removes it.-Mus.
a lot of paper, seen the bath nearly black, but the

Vicar" adopt the plan of cutting his stencil plates ont
of thick foil (an alloy of lead and tin)? If so, great
[2070-STENCIL PLATES.-Does our friend" The
lines. In cutting a fresh stencil plate even from the
freedom may be gained even in the repetition of the
same design by departing from the strict geometrieal
type has been used for the purpose named in Leipsic,
be exaggerated to give greater ease. Metschroma
old pattern, an apparently accidental deviation may
but there is none of the richness of colour obtainable
obtainable at shops in Oxford-street on either side of
by stencil colouring as to decalcomanic transfers are
the Regent-circus; but the writer has never seen any
melting together about equal quantities of common
subject suitable for the purpose named.-S. T.
black pitch and rosin. When thoroughly melted, a
[2072] PITCH. - Shoemaker's wax is made by
compound. The quantity of oil depends on the season
small quantity of a common oil is added, to soften the
of the year, more in cold and less in hot weather. To
make it lighter in colour it is drawn out by the hands.
An article called prepared pitch is now sold by the
added.-CRISPIN.

in spirit, or a coating composed of mucilage of traga- have been published on "Measuring Timber," but trade; it merely requires to be melted, and the oil

canth and sugar. I have repeatedly been told that the intestinal tube, and have been passed unaltered coated pills have passed through the whole length of through the system. leave your correspondent to judge what good they Under these circumstances I had done. A plan which I myself have found very efficacious is to screw each pill tightly up in fine tissue paper or cigarette paper, cutting off the superfluous material. A similar plan is adopted with balls for dogs and horses and I am glad to see the quotation from "Montaigne The ENGLISH MECHANIC improves, restored to the head of the Correspondence columns. -ARTHUR W. BLACKLOCK, Newbridge, Hardgate, Aberdeen.

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[2043]-PILLS. First see that your pills are thoroughly dried, then stick each with a pin the head of which is bent down like a pot-hook f; now dip the pills one at a time in a strong solution of gum arabic and hang ou a string to dry in a warm place. This will not only render the pills tasteless, but prevent the deliquescence some kinds are subject to.-S. T. [2013]-PILLS.-If "Wry Face" will apply to any chemist, he will find that his grievance can be remedied without much trouble or expense.-BETA.

[2063.]-MEASURING TIMBER.-Numerous works whose everyone wit accustomed to use. I have been generally speaking one work is as good as another. Aitkin's tables are as good as anybody's. Cost I think for sometime in the timber trade, and find that 4s. 6d.-GITCHE MANITO.

Of course will recommend his own or the one

have one in daily use that was repaired some months
e., free from baryta, its common adulte rack or two.
ago with white lead. The white lead must be good
T
lamp must be laid aside for at least a week or

[2073.]-CEMENT FOR PARAFFIN LAMP-I

should obtain "Hoppus's Measurer," price about 28. It
[2063.]-MEASURING TIMBER.-R. Livingstones.
may be obtained at a second-hand book shop for con-
siderably less.-JONATH.

of vibrations per second, of the mean rays of the seve-
[2004]-QUESTION ON LIGHT-The numbers
ral colours of the spectrum are, in millions of millions
indigo 686, violet 728.-ERNEST.
Red 497, orange 528, yellow 529, green 601, blue 648,

gamate zinc plates, clean thoroughly with diluted
muriatic acid; pour the mercury on, and spread it
[2066.]-ZINC PLATE FOR BATTERY.-To amal-
over with a brush; allow them to drip, and they will
thickness answers the purpose as well as any other
be ready for use. The best sheet zinc of the requisite
kind.-J. E. V., Edinburgh.

[2046.]-GYMNASTICS.-The following works are [2066.1-ZINC PLATE FOR BATTERY.-Had recommended:-" Gymnastics," by Chiosso, price 18. "G. Deku" put in practice the slight knowledge he 6d., Walton and Maberley; "Course of Gymnastic would have found the practical part of it so easily acExercises," by Rolland, price 88. Gd., Oliver and Boyd;quired as hardly to need troubling the MECHANIC for seems to be in possession of in regard to his query, he "Roth's Movements or Exercises," price 18.; "Ling's information upon so simple a matter. Gymnastics," by Koth, price 2s. 6d., Groombridge. commercial sheet zine will do, procurable from any BETA. [2049.]-LANTERN LENS.-A single plano-convex the acid solution with a piece of rag or a brush, pour The ordinary metal warehouse. After scouring the plate clean in rubbing "G. Deku" will find the mercury spread itself upon it a little mercury, and by still continuing the evenly over either side of the plate, making the amalgamation of the plate, if a matter of question, one of very little difficulty indeed.-H.

lens would do, but the result would not satisfy you. Many cheap lanterns are nearly useless on this account; go to a little more expense to purchase a double condenser, or if you have a good fint planoconvex, get an optician to adjust another to it. Write to Cox, of Ludgate-hill, or any practical optician.C. WARD.

[2049.]-LANTERN LENS.-If "Lime Light wishes to have good results from his magic lantern, I would recommend him to use the double combination 3in. condenser.-J. E. V., Edinburgh.

[2053.]-BEECH.-Expose the wood to the presence of steam in a covered vessel for a few hours, then withdraw it and allow it to dry slowly. It should be under pressure of some degree, even if not more than 1 or 2lb. to the inch.-S. T.

[2054.]-HYPOCHLORIC ACID.-Such an acid has not yet been discovered. The only oxygen acids of chlorine are:-Hypochlorous acid, HCIO; chlorous acid, HCIO; chloric acid, HCIO,; and perchloric acid, HCIO-ERNEST.

over his plate by adding a little of the pure acid and
[2066.]-TO AMALGAMATE ZINC PLATE FOR
then rubbing itoverwith a piece of tow or waste cotton,
BATTERY.-G. Deku can make the mercury flow
then well washing it in plenty of water.
A. A. A.
get on, will he write to our ENGLISH MECHANIC -

[2075.]-WATER-PIPE SWEATING. The supposed sweating is a condensation of vapour or almospheric moisture on the surface of the pipe from the lower temperature of the water contained therein.

-S. T.

send you diagram of Varley's patent coils used in Pest
[2079.]-VARLEY'S PATENT COIL.-Herewith I
Office instruments. It
is same size as the

difference in this coll
is the needle
coil itself. The only

and

the injurious effects
the two permanent bar
magnets, which stop
coil. It works exceed-
of lightning upon the
ing well, much quicker
If" H. R. H." wishes,
I will send him a
than the old system.
keys used in these in-
manent bar magnets, B
diagram of contact
struments. A'A' per
and south poles as
needle which has north
marked, C C coils, D
pinion of needle.-W.

GOLDING.

N. S

c

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S." will look at my
recipe for phospho-
RUS.-If
[2081.]-PHOSPHO-
"M. P.
page 588 [1760], he will
If he cannot rus paste in No. 257,
rus does not require
see that the phospho-
powdering. The proof
spirit will do that
quite sufficiently.-GITCHE MANITO.

this, multiply the square of half the diameter by
[2068.]-CONTENTS OF IRON PANS.-To find

2 335

355

113

and by the height. For instance, the first pan contains:
11 × 11 × 355 × 11
2 x 2 x 113 x 2

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X -x 58 6in. -
113

=

[2055.]-COIN.-The piece, as per engraving, is a of a globe, multiply the cube of the diameter by 0 5236. phosphorus, on pouring off the S. V. R., sufficiently

[2081.-PHOSPHORUS. — If "M. P. S." introduces into a florence flask 1pt, phosphorus and 8pts. of rectified spirit, and heats in hot water until the 522 cub. ft. 118 cub. in. To measure the eubic contents hitting cork) agitates briskly till cold, he will find the phosphorus has melted, and then (inserting a well

issued in 1618. The weights were issued by Royal proclamation from the Royal mint, ard the chief officers

-ERNEST.

weight of the double crown of James 1st. There are others of various weights according to the denomination of the gold coin, the unit 228., the crown 5s. 6d. the thistle crown 48. 44d., the half-crown 2s. 9d. I solidity of a sphere or globe multiply the cube of the [2068-CONTENTS OF IRON PANS.-To find the unfermenting paste.-A. P. S. fine for paste." See Beasley, p. 393, for an excellent have standard weights of all the above, as also those diameter of the sphere by 5236, and the product will employed for the granitic paint is silicate of potash, [2084.] GRANITIC PAINT. The menstruum be the solidity. To find the solidity of the segment of which is supposed to harden the pigment with which in all cities, boroughs, and town corporate of England the base of the segment, add the square of the height, neither of which points are, so far as my experience a sphere. To three times the square of the radius of it is admixed, and combine them in a durable manner, and Wales were commanded to provide such weights and this sum multiplied by the height and 5236 will and scales as provided by the master of the mint, and give the solidity.-JONATH. all persons were forbidden to have or use any other weights for the gold coins. Vide Ruding's," Annals of the Coinage," page 374.-D. T. BATTY, 9, Fennellstreet, Manchester.

[2055]-COIN OR COUNTER-In answer to Mr. Smith, the engraving represents a card counter. I have a similar one in my possession, with Vs. VID., instead of XIS. English coins were made of tin and copper, and now are of bronze, but brass ones were never struck.-HENRY W. HENFREY, M.N.S., Markham-house, Brighton.

[2057.]-ZINC PLANT-Form a feeble solution of acetate of lead, suspend in it a piece of zinc and some brass wires, the latter represent the branches of the tree.-ERNEST.

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goes, successfully attained.-S. T.

[2097.]-STAINING WOOD.-F. Drop probably has not given his work coats enough of stain to overcome the blue colour he speaks of. If the stain is made properly, this is the reason of its not being black enough; he must do it several times, until the blue colour is overcome. If this does not succeed, I will give him, through our MECHANIC, a recipe that will answer on his requiring it.-GILDER.

[2097.]-STAINING WOOD.- Drop a little sul phuric acid into a small quantity of water, brush over the wood and hold to the fire; this will produce a fine black, which will receive a good polish. Or take pt. of vinegar, 1oz. of dry lamp-black, 6oz. of iron rust sifted; mix and let it stand for a week. Lay 3 or 4 coats of this on hot, and then rub with linseed oil, and you will have a very deep black.-MINNEHAHA. probably die black [2097.]-STAINING WOOD.-I think if F. Drop leather, and might be so with wood. were to give the wood a strong solution of salts of worth the trial.-AB INITIO. tartar before applying the copperas, it would very This process is effective with I think it is [2102.]-VALVE.-I have used the annexed for s

tents of a pan in the shape of the annexed sketch, can be found as [2068.]-CONTENTS OF IRON PANS.-The conof the depth F G; and this A follows:-To three times the square of the radius C F, add the square sum multiplied by the depth again by 5236, will give the and the product of the diaG, and the product solidity of to the sum of their squares; the bottom; meters A B and C D, added tiplied by the depth E F and and this sum being mul[2057.]-ZINC PLANT. The zinc plant can be the solidity of A B made by "A Late Subscriber, E. S." by twisting a which, added to the solidity again by 2618, will give piece of wire round a lump of zinc and inserting one of the bottom, will give the contents of the pan teD, end in the cork of the bottle; then attach other pieces quired. To find the cubic contents of a globe multiply of wire to the zinc and twist them in any form he may the cube of the diameter by 5236, or the cube of the think proper; some put a little chins doll in between, circumference by 016887.-J. LINTON. and beads of various colours, which has a curious effect; then fill the bottle up with water so as to there is no stated amount of alcohol used for the pur cover the zinc, and put a little sugar of lead in, and let it stand perfectly still; the tree will begin to [2069.] PHOTOGRAPHY. In reply to "Lex," A pennyworth of sugar of lead may be obtained at any chemist's-enough for 3 or 4; it will cause a white cloud, which clears off.-A. A. A. [2057.]-ZINC PLANT.-This is easily prepared by suspending a piece of granulated zinc in a strong so lution of acetate of lead. In a short time beautiful plates of lead will form upon the zinc, and increase the solution (after sensitising) into the bottle wherein model engine, which is a rough sketch of my own.

grow.

till the solution becomes exhausted.-BETA.

should advise him not to use it at all. With some
samples of paper I have found that it tends to blister
pose he speaks of-merely a few drops or so; but I
lated spirit.
the paper, whilst with others I believe it almost pre-
altogether, either the spirit of wine or the ether, both
vents it. In no case, however, should I advise methy-
being impure. My method of working is to pour back
That is best out of the operating room
is some kaolin, and the next time that I want to use it J.W.

LINK

HARCH 25, 1870.]

09.]-ALUM AND IRON TANKS.-If "Amar Dyer" uses his iron tank to boil alum in, he will stroy the tank, waste his alum, and spoil anything be immerses in it. Alum acts strongly on iron, and Bould be boiled either in lead-lined vessels or in eod by means of a lead steam-pipe. Lead vessels are employed in alum works.-SIGMA. [2121.]-BOILER TAP.-"R. A." should unscrew the screw at the bottom of the plug; take out the plag, and grind it in with emery and oil until he sees it bright in every part: then screw it up again; this may stop the leaking. To get it out, put a lever in the bib, and unscrew. Fix a new tap with lead collars. red lead, and whitelead. -GILDER.

continually in water, and I am told the water has no effect upon them.-NON-ADHESIVE. [2144.]-FELT AND AMADOU PLASTER-Will some one describe the modus operandi for covering the surface of felt and amadou with isinglass, &c.?A. P. S.

[2145.]-REPOLISHING A VULCANITE WATCH CHAIN.-Will some kind reader inform me how to repolish a vulcanite chain which has become deadlooking with wear, so as to make it like jet again?— A COUNTRY VICAR.

[2146.-VENEERING.-Will one of your subscribers kindly inform me how to vencer a table, &c., and the tools required ?-H. E. D.

[2147.)-BENNETT'S CHUCK.-I would be much obliged if J. K. P." would explain Bennett's chuck for the benefit of myself and fellow readers of the MECHANIC. Also if he would mention a way of keep ing the mandrel of the lathe still when using the division plate and index.-KENNINGTON AMATEUR. [2148.] TALLOW. Will some brother reader describe the best system of refining ships' grease into tallow?-YOUNG BEGINNER.

[2149.]-SURVEYING.-Can any reader tell me what book will give the best help to make surveys and valuations of dwelling houses and land to be mortgaged to a building society?-READER. [2150.]-LIGHTING GAS LAMPS BY ELECTRICITY-I have heard that a means has been discovered of lighting street gas-lanips in a simultaneously with electricity. Can anyone tell me if such a system is in operation, now, where and how it is done?-CANADIAN.

to make a good paste or cement for clothing iron rollers?-T. SIMMS.

[2162.]-SEAMS OF MACINTOSH.-Can any fellow reader tell me what is used for joining the seams of a macintosh or waterproof coat?-G. W. D.

[2163.]-LEATHER BAG MAKING.-Would some one tell me how to make small leather cases-such cases being made of paper and covered with leather by gluing the leather on the paper cases-such as are now used by ladies and gentlemen ?-T. H. P.

[2164.] PHOTOZINCOGRAPHY.- Will some of your intelligent correspondents be kind enough to favour me with the titles of some of the best books on subject of photozincography and anastatic printing?-I desire to know the ins and outs" of the printing.-W. H.

the

[2165.]-WORKING MEN'S EXHIBITION.-Can

any correspondent say if any employer is eligible to exhibit an article of his own invention in the forthcoming Working Men's Exhibition, and say to whom to apply for particulars?-MORELIGHT.

[2166.]-MAGNET.-Can I make a magnet by battery power? Will Smee's battery do; how many cells? My magnet is 7in. x lin. x fin., horseshoe-shape, tempered steel.-J. GABELL.

[2167.]-LATIN.-Can any brother reader inform me if there is a system for self-teaching Latin; where I could obtain it, and what would be the cost?-A NEW

SUBSCRIBER. town

[2151.]-HARDENING MILL BILLS.-Will any reader inform me how mill bills for dressing French stones are hardened, and what is used for hardening ?T. MARSH.

[2152.]-PAINT ON BICYCLES.-I wish one of your many subscribers would answer me these questions:-How is paint put on bicycles?-is it common oil paint ? and what gives it the glazy look? Is it some kind of varnish-A SUBSCRIBER.

[212]-WOOL.-In reply to "J. F. F.," I can explain to him the following German names:-Holz wolle, woodwool, is a wood reduced into powder, and employed as velvet powder for making flock paper; waldwolle, forest wool, pine wool, or pine Deedle wool, is a fibre obtained in Prussia, Holland, &c.; by treating the leaves of the Pinus sylvestris, c., with a solution of carbonate of soda, this fibre is used for stuffing mattresses, making blankets, &c.; an etherous oil, an extract, and a soap are also obtained from this fabrication; flannel impregnated with this essential oil is preconised against rheumatism, &c. Kunstiolle, artificial wool, is the well known shoddy. The name of vegetable wool is also given to several fibres, viz,, the jute (Corchorus capsularis, textilis, &c.) of the linden order, or Tiliacea; the down of the lanero, corkwood (Ochroma lagopus); the down of the different kinds of Eriodendrom; these two last belonging to the Sterculia order, &c.-BERNARDIN. [2136.]-DIVIDING PLATE.-In answer to "Bierlala," if your plate is a lathe pulley, and you have room for only, say six rows of holes, you will what I have on mine, viz., 360, 108, 100, 96, 84, 24 (the last for hard usage to save the others), as good numbers as you can have. If you want to do ornamental work by the double counting" of Captain Ash, then you must have 192 instead of 96. If you want large strong holes, and cannot get in 360, then 240, 192, 140, 135, 100, 72, are useful numbers. That was the last I made. Be fore that, I made one for my own use of 300 outside, [2153.]-VERTICAL SAW FRAME.-Would some then 11, 13, 14, 17, 19, all in one row, with 216, 140, 96, fellow reader give me some information on saw 84 inside of that. If your plate is flat from outside to frames? I have some large oak trees 2ft 8in. through, centre, you can get in many more in the diameter you and I intend to put a frame to cut them. Explain mention, and I consider one of 13 rows, that I once the different parts and what strength to make them made, complete enough for most practical purposes.it will have to cut 3ft. logs down to 1ft. 4in.-to take The one of the cutting engine, figured this week, has in any number of saws up to fourteen. Also the best 37 rows containing every number up to 100, and way of fixing the logs while being sawn-the logs are ranging as high as 366. Good gunmetal is much bet- mostly round, and will want good fixings. Give the ter than brass. I get mine at Bowen's, Dorrington-length of stroke. The weight of foundation required. street, Coldbath-square. Ask for best gunmetal. -J. T. W. have serious thoughts of taking the gunmetal pulley off my lathe, and putting on a cast-iron one, as the Division pegs, or "index pegs." are, in my opinion, always made wrong. Go to Wilkinson, by all means, if you want something firstclass, without being ruined. It is a chance if it did not come to him at last, if you took it anywhere else to get it done. Say your outside row is in. from and state number edge, and distance between rows 32, of rows you want, and direct to me at Pitcairn's, Library, King's College-road, N. W., and I will write out a list for you.-J. K. P.

holes will last better.

5

1

(2137.)-PITCH PINE WOOD.-" Pinaster" had better get some of Stephens' wood stains. The cause of the wood looking opaque when stained is, the staining material has more body than it ought. Very good stains can be made of burnt sienna and Vandyke brown, in certain proportions, but Stephens' are more transparent. I see the "Welsh Shepherd" recommends one coat of oak varnish. Is he aware that it will not stand long out of doors, and some of it is the veriest rubbish possible. Stick to the boiled oil for the outside, two or three coats of it; never mind heating it; if heated look to your brushes, or you may get them burned up by the hot oil. "Pinaster" may depend upon this information, as I have had experience for these last 21 years as a house decorator. All wood stains do not get darker in course of time; of that I am quite positive, and do not wish to mislead-GILDER.

[2138.]-HARDENING MILL CHISELS-I advise G. Doubleday to coat his mill chisels with finelypowdered pu siate of potash, make them red hot, and plung them into urine; then brighten and temper.-AS INITIO.

NOTES AND QUERIES.

[2154.]-HARMONIUM-TO "ADEPT." I am

trying to build a small harmonium with two rows of reeds to represent four stops, and I should esteem it a great favour if our good friend "An Adept" will advise me which are the best reeds to purchase for a small instrument, also where I can purchase them, also if the feeders will act as well on the bottom board of case; if so, that will save me much room? I also should be much obliged if he will favour me with a sketch of his silent feeder valve for bellows that was named in

[2168.] DIMENSIONS OF MODEL STEAM ENGINE.-Will some brother reader give me the dimensions of fittings for a model steam enginecylinder 3in. stroke, 14in. bore? What size steam pipe should I require, and length of lever for safety valve ?-R. R.

[2169.]-PROBLEM.-Draw a line D E parallel 'to the base B C of a triangle ABC, so that DE is equal to the difference of BD and C E.-P. B. McG.

[2170.]-AN UNANSWERED QUERY.-Will some correspondent tell me how to blacken old copper coins? This query was asked some time since, but has not yet received any answer.-GITCHE MANITO.

[2171.]-BORING MODEL CANNON.-I beg to return my sincere thanks for the instruction furnished on the above subject. Being unable to make the halfround boring bit referred to, will either of my kind instructors be good enongh to inform me where I can obtain the same?-J. S.

[2172.] BINDER'S ANSWERED QUERY.

CUTTING PRESS-UNWill anyone oblige by

giving a description of cutting press referred to by J. J. A.," query 1467? I can bind first-rate, but cannot cut with an ordinary knife. It would no doubt confer a boon on many of our readers.-MASCHIL. [2173.]-GAS'WORKS.-Will" Rotherwood" be so kind as give a few more particulars about his economical gas works in Reply 1731, p. 613, as to construction and operation in gas manufacture; also where the E. G. works are to be had?-JOHANNES.

[2174.]-MAGIC LANTERN AND MICROSCOPE. -I have a magic lantern with 3in. condensing lenses, and should be glad to know what would be the cost of a good microscope to attach to it-suitable for showing animalculæ in water, &c. Would a powerful lens, to burn camphorated paraffin, give a disc of light suffiJanuary 14, as my valves make more noise that I like ciently large and clear to show microscopic objects to an audience? Could the same instrument be so ad[2155.]-LACTARME OR MILK ALBUMEN.-justed as to be used in the daytime as a solar microHow can I make this in a dry state, so that it wil keep similar to the albumen of commerce, that is in flakes very like shellac ?—LAC.

to hear.-W. D.

[2156.J-ZINC ASHES.-What are zinc ashes, where can I purchase them, and what is the price per ton? -ELDER KIN.

[2157.] AN INSTRUCTOR FOR PLATELAYERS.-Will some of our brother correspondents inform me where I can get a book that will instruct me how to set out a rao us of any dimension-say from one chain to one mile, and the proper distance from a pair of points to a crossing of say one in two upwards? What I mean is the correct radius from the points to any spread crossing for a permanent way, I think there is a book as an instructor for platelayers?-UNLEARNED PLATELAYER.

[2158] ARTIFICIAL LEG. Will some kind brother give me the drawings, and inform me how to make an artificial leg below the knee, and what is the best material to make it of?-W. R. E. [2159.-CLAMS.-Will any reader show me how to construct a pair of clams for splicing or jointing leather-such as those used by roller coverers? A diagram will greatly oblige.-T. SIMMS.

[2160.]-PRESSURE ON COLUMNS. — Will any brother subscriber tell me how many tons' pressure (2139.]—HARMONIUM.-Would some kind reader four iron columns will bear standing upright as shown,

State how many rows of reeds I could have for an harmonium, the case of which is the size of a fiveOctave Alexandre's make? If some one would state how I could fit it up with two rows I should be much obliged, and, likewise, what kind of reeds, &c. would le required, as I am entirely ignorant how to proceed; but having made the case, bellows, &c., I want to finish it.-J.W.

[214]-POOR LAD'S QUERY.-Will some kind astronomieal reader advise me? Having but very limited means, I thought of purchasing one of Wray's 24in. object glasses, price £2, but seeing in our last number that a 5in. specula would cost the same, I am rather in a fix which to have, and should esteem it a favour for a good opinion.-A POOR LAD.

[2141]-SPLITTING QUILLS.-How can I split quills in half-I have tried several means without success? Should the quills be soaked or softened ?— CROWQUILL.

2142-SOFTENING CAST IRON.-Can I soften cast iron before turning? I have a face-plate to turn; being so hard, the tool will not cut it.-G. B. K.

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in plain figures ?-W, R. E.

3/2

SOLID

scope ?-FRAYER.

[2175.]-LIFTING POWER.-Has the wedge or the screw jack the most power in lifting ?-T. H. H.

[2176.]-BLAST FAN.-I would esteem it a favour if one or more of your readers would give me some information as to the construction and arrangement of a blast fan suitable for a smith's forge fire.-C. T. [2177.]-PROBLEM.-With a point in the perimeter of a given circle for a centre to describe another circle, an arc of which shall divide the given circle into two equal parts.-INDAGATOR.

[2178.]-CIRCULAR DISC.-What must be the size of a circular disc to be fixed on its centre in the boundary of a circular orifice 1ft. in diameter, so that exactly one-half the area of the orifice is covered by the disc ?-INDAGATOR.

[2179.]-GRINDING SPECULA.-Will steel, iron, and metal make a tool to grind and polish glass specula? For the purpose are the grooves cast or cut in the grinding tool? Can a glass speculum be ground, if firm, level and stationary? Is it possible to grind a speculum parabolic without first grinding it spherically?-ANDREW JOHNSON.

[2180.]-ENGINEERING IN GERMANY, &c.-Is there a mechanical or engineering school or college in Germany where pupils are instructed in practical as well as theoretical engineering, and where? Thanks to Mr. Biggs for his answer to query 1934, and may I ask him if he will kindly furnish me with a solution of the following, which appeared in the Science and Art Department examination papers a few years back? If an arc of a circle measure 50ft., while the radius is 18ft., what is the area of a sector whose base is the given arc ?-Y. P. W.

[2181.]-DERBY CEMENT.-Will some one oblige me with a recipe for Derby cement for mending jet, vulcanite, china, or glass ?-G. S. H.

[2182.]-CONSTRUCTING COILS.-I am about to make a coil, and intend to use about six miles of No. 36 copper wire covered with silk for the secondary. I want to know what length of No. 16 cotton-covered copper wire I should use for the primary, also about what number of sheets of tinfoil 1ft. square would go to the pound? I also want to know what length of spark I could get from the coil, also how many of the bichromate of potash bottle-batteries ought I to use? Is wire, covered with composition, better than silk or cotton-covered wire, or would wire, covered with cotton first and then with the composition, be still better? Is there any substitute for gutta percha tissue, and what kind of cotton or silk is used for covering the wire in shops where it is sold covered? These last three queries I have often seen asked, but

2143-GLUE TO RESIST WATER.-Could you
sell me of a glue that will resist water, or of any com-
portion for fastening wood together, so as to resist
water? There is a firm in London, I think, who make
Mucks for carpet printers; these blocks have to be put ROLLERS. Will any reader please to tell me how have never seen them answered.-NEMO.

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IRON

[2188.]-TAXIDERMY. – On application for the work mentioned by your correspondent, I find that it has been out of print for 20 years. Can anyone inform me if there is any other published, and who by ?

SOLD.

[2184.]-SULPHATE OF

LEAD BATTERY.-I will feel obliged to any of your readers who will be so good as describe how these batteries are made. understand Moseley's patent battery consists of copper I cups tinned, and fixed on a central wire. Is it actually necessary to have the cups so tinned? and is a porous cell requisite? Would a solution of sulphate of lead not do to charge Smee's cells with? promised a description of all batteries now known or "Sigma" has used, but it may be some time before his papers bring him on to that part of the subject, and in the meantime many of your readers as well as myself may be NULLA FIDES.

focussing s'ide of the above telescope? 3. What will
will be the probable cost of putting a rack on the
be the best and cheapest way of mounting one of
Solomon's £5 telescopes on a stand, the legs to be
made shorter when not in use? Perhaps "Pollux,"
on p. 604, will be able to give some information about
a suitable stand for a working man's telescope, as he
they cannot afford the more elaborate and costly work-
seems to know what they have to put up with when
manship of an Equatoreal stand, viz., the primitive and
uncomplicated mechanism of a brick wall, and the
elevation, depression, and sideral motion of the instru-
ment as to be performed by muscular power ?—H. F.
Will any of our friends, having experience in such
[2200.]-ENGINE AND BOILER FOR LAUNCH.-
engine and boiler is best calculated for driving a
matters, kindly inform me what style and size of
pitch of screw, and probable cost ?-SOLICITOR.
inform me how to make a cheap and simple steam
[2201]-STEAM ROARER-Will some kind reader
roarer to act in place of a bell for a mill? I should
also like to know if it is obliged to be made of brass?
There was a plan of a steam whistle in the ENGLISH
act, so I wish to have the plan and dimensions of one
MECHANIC a short time back, but the drawing was
very small.
I failed in making one off it that would
of those sort called a roarer, which are so much used
now for works.-YOUNG ENGINEER.
wheel skates?-C. FRANCIS.
[2202.]-WHEEL SKATES.-Will
reader kindly inform me the best plan for making
some brother

[MARCH 25, 1870.

is mixed? and also how to mix the paint for striping? -YOUNG PAINTER.

-Our ENGLISH

MECHANIC has spoken several times of Cowrie money
[2217.]-WHAMPOOM MONEY.
formation on the Whampooms of North America-
or shell money. I should feel obliged for some in-
PIONEER.

[2218]-GEOMETRY-Is there any geometrical means for proving the following theorem?-Having three circles on a plane, and drawing tangents common to two, those common tangents have their latersCtions on the same straight line.-X. X.

give me a few details on the modern methods of
[2219.]-SILICIOUS GALENA.-Could some reader
reducing silicious galena, also on the substitutes for
nitro-glycerine (blasting purposes)?-FEU FOLLET.
[2220.]-SOLDERING.-I want to solder a 2in. cast
tinning the cast iron pipe. Can any friend inform
me how I can do it ?-G. D.

at a standstill for want of the information. -FRONTI launch 36ft. long by 9ft. broad, with number of blades, iron pipe to a 2in. lead pipe. I find a difficulty in

[2185.]-MILDEW ON ENGRAVINGS. feel much obliged if one of your correspondents will - I shall inform me how to remove mildew from picture prints, and how to prevent it.-CONSTANT READER.

to

[2186.] BAROMETER "Jonath" for his information on the safety valve. TUBES.- Thanks I have some barometer tubes (new ones), and in laying by they have got covered with a film inside that makes the mercury look muddy when it is put in. Can anyone tell me the best way to clean them?-COMPENSA

TION.

[2187.]-NAPHTHA AND GAS TAR.-Would any brother subscriber give instructions naphtha and anything else that can be made from gas for making tar, with a description of vessels, &c., required for the same? About 80 gallons of tar is as much as I intend to use for that purpose weekly, which will, perhaps, give an idea of the sizes of what will be required.

J. H. M.

[2188.]-ORNAMENTAL WOOD AND METAL CUTTING MACHINE AND

VELOCIPEDE.

Having for some time seen advertised in our paper Cunningham's fret-saw, drilling apparatus, and kinograph, I should like to have the opinions of a few of our subscribers who may have tried them as to whether they are useful machines, well made, of good metal, worth their price, and, in short, all they profess to be. I should also like the opinion of some of our velocipedists if in every case a driving-wheel above 36in. ceases to be an advantage. I have an ordinary 36in. and 33in. bicycle, but I want to get nearer the ground, and I think of reversing it, so bringing the small wheel to the front and making it the guiding wheel, and putting the wheels farther apart and driving it by a crank working in a bearing between the wheels, and communicating with the driving wheel (the hind wheel) by a connecting rod as outside a locomotive; or with a pedal working like the elbow joint of a bell-pull and connected as before: shall I use my old wheels, or have the driving-wheel larger-say eft., and, perhaps, the front wheel smaller -say 2ft., and which driving-gear shall I use ?-GIM

CRACK.

[2189.]-CIRCULAR RAIL.-Can any reader inform me how to make a circular rail for a model locomotive? It must be constructed on a framing of some sort, so that I can lay it on the floor of a room without injuring the curpet, &c.-F. G. C.

[2190.]-THE ORGAN.-Can any brother reader tell me the way in which an octave coupler is made? also how a composition pedal is connected to the stops? A drawing of each will oblige.-ORGANINE.

[2191.]-TURRET CLOCK.-Would Mr. Maddison kindly inform me what advantage he gets in the use of cast iron wheels in his clock instead of brass-most generally used? I never saw one erected successfully with iron wheels. I should think that an iron wheel working it a pinion of iron or steel would work harshly together, and also be liable to stop through rust collecting between wheel and pinion.-TINTAC.

[2192]-SULPHATE OF AMMONIA.-Would Mr. G. Davis, or some other among your talented correspondents, inform me of the most improved and simplest way for finding the degree of strength of sulphate of ammonia ?-BASIN.

[2193.]-FINE CHARCOAL.-Can any subscriber inform me where I may obtain fine prepared charcoal for rubbing down silvered circles, &c. ?-it is generally in short square sticks.-TERMUS.

[2194.]-INTENSITY COIL.-Can any fellow reader inform me how to make a small intensity coil powerful enough to fire gunpowder?-COIL.

[2195.]-SMOKELESS LAMPS.-Would Henry W. Reveley, Rending, who sends a sectional drawing of smokeless lamps without a chimney, in your journal of Jan. 21, 1870, kindly furnish particulars as construction, length of cone and hollow globe, and how the wick is raised or lowered?-PRACTICAL.

to

[2196.]-NAMES OF PUBLISHERS.-Is there a book published entitled "Annals of the Wars of Eng

trying to fit up a small machine so that I can run down
[2203]-FLOUR DRESSING MACHINE.-I am
machine is broken down, and occasionally a few grists.
a few sacks of seconds flour whenever my other
I have made a 12in. cylinder which will take three
number of wire ought I to use, and how many brushes,
sheets of flour wire and one of sharp wire? What
and what fall ought the cylinder to have ?-A COUNTRY
MILLER.

placed upon it; what will be the height of water in the
[2204.-PROBLEM.-The diameter of the plate of
a hydrostatic bellows is 12in., a weight of 250lb. is
pipe?-W. B. S.

[2205.]-PROBLEM.-What is the atmospheric pres-
sure when the barometer stands at 30in. ?-W. B. S.
[2206.]-CERAMIC MANUFACTURE.-Thanks to
inquiring, however, at Barth's and Quariteh's, I find
"Beta" and H. B. Miller for their information. On
Are there different editions at different prices? It is
that instead of 208., 289., &c., Brongniart's book is 568.
not needful that the works sought should be in French
a good practical English or French book at a
moderate charge, especially if treating on the prepara-
tion of colours for painting, and printing, is what I
require.-IOTA.

made? I have tried my hand at one several times and
[2207.)-CRICKET BATS.-How are cricket bats
failed?-A SUBSCRIBER IN CANADA.

detail the process of refining with chlorine: would he
[2208.)-REFINING BEESWAX-Some time ago
"Feu Follet," in reply to "Pulp Maker," offered to
please do so, as I wish to try my hand at it?-A
COLOURMAN.

[2209.]-OVERLAND ROUTE.
is also via Southampton, the
explain why, if the Overland route via Marseilles
Will "Selwyn"
Marseilles 18., via Southampton 9d.? How do the 9d.
"Postal Guide" makes
the distinction of the routes for letters, thus-India via
cnes go?-IOTA.

Proctor or some obliging correspondent to be kind
[2210.]-BAR MICROMETER-Might I ask Mr.
enough to favour myself and your innumerable
astronomical readers with a drawing or description of
uses? What is the difference in use between it and a
a bar micrometer and its field of view, and explain its
ring micrometer?-IOTA.

[2211.]-OBJECT GLASSES.- Referring to Mr.
Purkiss's letter on t's subject in the ENGLISH
MECHANIC for March 4th, might I ask him to be kind
to have been divided by Mr. Buckingham's instrument
enough to say in what year he knows 72 Andromeda
with a power 2? and also if he can inform me how

many seconds apart they then were, and how many
at the present time?-IOTA.

[2212]-SPIRAL SPRING.-Is the spiral spring
that steel springs are only useful within narrow
reliable as used for steam pressure gauges? I presume
limits-say a range of 40lb. or 501b. What I want is
extremes I have stated.
an extremely accurate means of registering pressure,
by communicating the pressure to a hand travelling
increasing by a pound at a time, between the two
I suppose this might be done
yard would seem the best way of applying the weight
round a well-divided dial, but my difficulty is in what
way to communicate it?
better?-F. Q. Q.
The principle of the steel-
for the division of the dial. Can anyone suggest a
[2213.]-STANWAY'S VELOCIPEDE.-I hope Mr.

for short sighted people?-ETHARDO.
[2221.]-SHORT SIGHT.-Are there telescopes sold

[2222.]-REDUCING LEATHER TO PULP.-Do that will reduce sole leather to a state of paste?— you or any of your chemical readers know of a solvent W. W.

[2223.]-ENGRAVING ON SLATE.-What kind of knife or graver is employed to engrave the lines and figures on a slate sun dial?-F.R. A.S.

[2224.]-BOILER-Thanks to "Vivas Sperandum "
for his kind answer to my query, but will be be kind
enough to give me a few more particulars?
50-horse power boiler per week (754 hours); pressure,
funuel as shown? 2. What would be the quantity for
I not put in the feed cistern at once without pipe and
1. Could
45lb.? The water is very much impregnated with
my brother reader ever tried carraqun in a boiler
lime; scale very hard-like porcelain almost. 3. Has
much incrusted, for my boiler is very intricate ?—UNE
IN A FIX.

brother reader kindly inform me if the exhaust steam
[2225.]-VACUUM IN CYLINDER. Will some
on leaving the cylinder of a high-pressure engine
against the full atmospheric pressure, or 15lb. on the
causes a partial vacuum, or has the piston to be forced
square inch?-VACANT HEAD.

it supposed to cure?-VACANT HEAD.
of iron used in medicine made, and what complaints is
[2226.]-TINCTURE OF IRON.-How is the tincture

could I make a life belt for boating purposes?—AVA-
[2227.)-LIFE BELT.-Where can I get or how

LONENSIS.

English brother reader give the full addresses of [2228]-ADDRESSES WANTED.-Will any kind some of the most important coal mines in Great Britain?-A FOREIGN CORRESPONDENT.

[2229.-WORKS ON CHINA GRASS.-I want some good works on China grass-either English, French, answer my query, stating purchaser and price, he will or German, &c. If a brother correspondent will much oblige.-A MELLIST.

fine old engraving, but, unhappily, quite covered with
[2230.)-REMOVING FLY SPOTS.-I have a very
fly spots. How can I remove them? I have tried
several ways, but failed.-PERA Y NO PERRA.

good enough to ask "Omicron" to explain what is
[2231]-ENCKE'S COMET.-Will you please be
meant by solving an equation by the method of least
squares an expression that occurs in his account of
Encke's comet ?-T. WAGHORN.

hunter's" Smaller Trigonometry," chapter X. :-The
[2232.]-PROBLEM.-Can any reader favour_me
hypothenuse A B of a right-angled triangle is divided
with a solution of the following problem from Tod-
at D, so that AD is to BD as CB is to CA. Show that

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how ornamental church windows are painted, and [2233.] STAINED GLASS. Will Mr. Josepb cept ingredients that are used? I know there is a Leicester or some other able correspondent inform me stained, as I have a little knowledge of some part, exand shading purposes called flux-it is mixed with reddish brown colour painted on the glass for opaque when it is burnt in a kiln it is very hard, and cannot turpentine. I want to know what it is composed of; be scraped off. I want also to know what ingredients colour or deposit on them, and when cleaned off leave such as yellow, blue, &c. For windows, as above, are used to stain plain glass in parts where wauted, have seen glass when taken out of the kiln with a red a beautiful clear yellow stain on the glass-according to the design painted on.-GUSTAVO KNOX.

What would be the most simple work on bell-ringing, pede by means of his feet as well as his hands? and Gregorian of 4in. aperture, and a power of about 103.

if not, I should like to know the name of the publisher, velocipede a description of which is given in the land ?" and if so, please name the publisher and price? Stanway will answer a few questions respecting his Will be give me his idea of the apparent diameter of and the price of the" Annals of the Wars of Europe." MECHANIC for March 4th. the publisher, and price?-H. G. REDDITCH. Does he propel his velocito be fixed between the levers, in consequence, there how does he manage to steer it, as the handle appears Is it steered with the feet or hands? What is the would not be room to get it round a sharp curve ? the method of steering, &c.; also what is the price of such a velocipede, and the name and residence of the distance between the front wheels? Please to describe

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tell me where he procured his 3in. refracting telescope [2234.]-TO "JUPITER."-Will "Jupiter" kindly Jupiter as seen by him with a power of 75! have of the ENGLISH MECHANIC, and what he gave for it? of which he writes in evident praise in the last issue this moment completed some observations with a than in. in diameter, nor could I detect more than a Jupiter certainly did not appear to me to be more good night. bear, and the mere suspicion of the "belts," but then it was not a "Jupiter" has seen with highest power? This will highest power his object glass will advantageously Will "Jupiter" kindly tell me the apparent diameter of the planet supply me with a point of departure from which I may deduce for myself other measurements.-FUIMUS. [2235.]-HOSIERY YARN.-How can I double and twist two threads of hosiery yarn from one to four per inch ?-TINKER.

[2236.]-DIRTY CEILING.-Can anyone tell mo space between them, which gives it a ribbed appearwhy the joists show through dirty ceilings, ie, whereance?-MINNEHAHA (GITCHE MANITO.) ever a joist is the ceiling is much cleaner than the

[2237.]-SALERATUS.-What is it ?-A. P. S. OF SPIRAL SPRINGS.-Would any reader kin y [2238.]-FORMULA FOR CALCULATING POWER

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