smoke as it passes from the roof to the cistern? The coal which is
burned here (bituminous) gives us a great deal of trouble in this
regard. A. The carbonaceous matters may be removed by passing the
water through a large barrel half filled with fine gravel and pounded,
freshly-burnt charcoal (free from dust), distributed in alternate
layers, each several inches deep. Over this spread a clean piece of
bagging, and fill in with fine gravel or coarse clean quartz sand for
12 inches or more. The inlet pipe should discharge at the bottom of
the barrel--the filtered water flowing from the top.
(20) F. E. H. asks: Can percussion caps be so composed as to explode
when pierced by a sharp pointed needle? If so, of what should they be
composed? A. Such an arrangement is employed in the needle gun. The
composition may be of mercuric fulminate.
(21) C. A. N. asks: What is the horse power of an engine 30 inches
stroke, 14 inches cylinder, 51 revolutions per minute, 60 lbs. mean
pressure in cylinder?
A. Piston area = 153.94 square inches. Piston speed = 255 feet per
minute. Indicated horse power =
153.94 x 60 x 255
----------------- = 71.4
33,000
(22) P. O. asks: If I admit steam 100 lbs. pressure in a cylinder 15
x 24 inches, and cut the steam off when piston has traveled 6 inches,
what will be the pressure at 6 inches, 12 inches, 18 inches, and 24
inches, or just before it exhausts? A. The pressure will vary about in
the inverse ratio of the volume, so that, approximately,
vol. of cylinder up to point of cut-off + clearance vol.
---------------------------------------------------------
vol. of cylinder at any point of expansion + clearance vol.
pressure above zero, at the given point.
= ----------------------------------------
pressure above zero, at point of cut-off.
(23) H. T. S. asks: What size should I make the holes in the side of a
fan wheel, 20 inches in diameter? Also what size should the nozzle
be? A. Allow an opening of from 17 to 20 square inches at inlet and
discharge.
(24) E. M. D. writes: I am constructing a telephone according to
directions in SCIENTIFIC AMERICAN SUPPLEMENT No. 142, using a bar
magnet in place of horseshoe magnet and soft iron core. 1. Would it
reduce the strength of bar magnet to cut a thread on one end of it?
A. No. 2. Will a bar magnet, used in Bell telephone, lose its power to
such a degree as not to work? A. Not readily. 3. Is No. 22 copper wire
of sufficient size for a telephone line of 1,000 feet? A. Yes; but
larger would be better.
(25) S. & Y. write: We have a pair of burrs on which we grind plaster.
The burrs are about 4 feet in diameter and 11/2 foot thick. We are
running them as an over runner at this time, but wish to change them
and make the lower burr run instead of the upper. Can a pair of burrs
of the above size be run in that way, and if so, what is the maximum
speed at which they can be run? A. If properly arranged, you can
run them, after the change, as fast as is allowable for overrunning
stones.
(26) J. J. asks: Which tire makes a wheel the strongest, 1.25 x 0.50
inch iron, or 1.25 x 5/16 steel tire? A. The steel tire will be the
strongest, comparing good qualities of steel and iron.
(27) E. L. W. asks: Is a ton (2,000 lbs.) of first class coke equal in
heat giving power to a ton (2,000 lbs.) of coal? If not, please
give me the relative value of coke and coal in heat giving power?
A. Calling the evaporative power of good anthracite coal 1, good
bituminous coal rates at about 0.92, and coke from 0.89 to 0.95.
(28) J. W. S. asks what to impregnate paper with to give it an
agreeable smell while burning. A. You may try a strong ethereal or
alcoholic solution of benzoin, tolu, storax, olibanum or labdanum.
To burn well the paper should first be impregnated with an aqueous
solution of niter and dried.
(29) M. G. asks whether hydrogen and oxygen can be produced as rapidly
and copiously in the decomposition of water by the galvanic battery as
by the action of sulphuric acid on zinc or lead in the one case,
and by heating chlorate of potassa in the other. A. Yes, with a very
powerful current.
(30) T. G. H. asks for names of useful treatises on mechanical
movements. A. "Scientific American Reference Book," and "507
Mechanical Movements."
(31) R. B. T. writes: We have just set up a new engine; the cylinder
is 8 x 12, has a common slide valve. We think the valve is too short;
it is set 0.125 inch open when on center, takes steam 10 inches before
cutting off; the exhaust is very free. The engine runs about 110
revolutions per minute. We think we could save steam by using a longer
valve, and cut-off about 5/8 stroke, and make the exhaust space in the
valve shorter, so that it will shut in a portion of the exhaust and
form a cushion for the piston. About how much of the exhaust can
we shut in without overdoing it? A. You can obtain a good action by
making the ratio of compression equal to the ratio of expansion,
with the proviso that the final cushion pressure must not exceed the
initial pressure.
(32) D. B. L. writes: Our boiler after being repaired was tested at
110 lbs. cold water pressure. Three days after it gave out where it
was repaired at 58 lbs. steam pressure. To find the leak we put on
80 lbs. cold water pressure, and could not find it. We then put steam
pressure at 40 lbs., which made the leak very great, whereas with
cold water pressure we could find none. Can you explain it? A. The
phenomenon is probably due to the change of shape in the boiler when
heated.
(33) F. C. writes: Our engine is a plain slide valve engine, 24 x 9,
steam following almost to end of stroke. How shall I make a valve to
cut off at 3/4? Our exhaust now is 1 inch, steam ports 0.75, bridges
0.75. Length of valve 41/2 inches, cavity 2-3/8, travel of valve 2
inches. Will I have to enlarge the steam chest; the valve uses the
whole length of it now? A. As the length and travel of valve must be
increased, it will be necessary to lengthen the steam chest, unless
you can apply an independent cut-off valve.
(34) T. P. writes: A small basement room 9 feet high is to be heated
by a furnace in an adjoining room. By carrying the hot air pipe
through the partition midway between the floor and the ceiling it will
stand at an angle of about 45 deg.. If carried through at the top of the
room it will of course be nearer vertical. In which position of the
hot air pipe will the room be most easily heated? A. Place the hot air
pipe in the position first described. Take the cold air from a point
near the floor through a flue opening above the roof.
(35) G. M. P. asks: What is a good and cheap substitute for salt for
raising the temperature of water to 230 deg. Fah.? A. An oil bath is often
used instead. Chloride of calcium will answer as well as salt, though
not so cheap.
[Illustration: Right Triangle--sides 15, 20, 25ft.]
(36) J. D. reminds us of an old and good method of drawing a
perpendicular to a straight line for the purpose of squaring
foundations, etc. From the corner of the foundation take two lines
respectively 15 and 20 feet, and connect them by a line of 25 feet;
the angle included between the two shorter lines will be a right
angle. The numbers 3, 4, 5, or, as in the present case, their
multiples 15, 20, 25, are taken to measure respectively the
perpendicular, base, and slant side of the triangle. It is obvious
that any scale may be used so long as the ratio of 3, 4, 5, is
observed.
(37) J. H. asks what kind of iron to use in making cast iron
armatures. A. Soft gray iron.
(38) F. H. C. asks: How can I etch cheaply on glass to imitate ground
figures or transparent figures on a ground background? A. For this
purpose the sand blast is now generally used; the glass is covered
with a film of wax or varnish, through which, with suitable needles or
gravers, is etched the design; a fine sharp silicious sand impelled
by a current of air is then directed from a suitable jet over the
prepared surface, and the etching is accomplished in a few minutes.
Glass is etched also by hydrofluoric acid; the plate may be prepared
as for the sand blast, and placed face downwards over a shallow leaden
tray, containing powdered fluorspar moistened with strong oil of
vitriol and gently warmed; the gaseous hydrofluoric acid given off
rapidly etches the portions of the glass not protected by the wax or
varnish. Hydrofluoric acid should be used with great care.
(39) L. H. writes: I have seen it asserted that the parasites that
infest the Asiatic tiger's paw are an exact miniature image of itself.
Is this so? A. No.
(40) J. G. B. asks if there is any way of melting brass in a common
sand crucible for castings of a pound or so in weight for a small
engine. A. You may melt small quantities of brass in any common stove
having a good draught, using a coal fire. You may use borax as a flux.
(41) F. & Co. ask: 1. In making a telephone as described in Figs. 4
and 5, SUPPLEMENT 142, must the diaphragm be entirely free, or can it
be punched and the screws which secure the flange pass through it? A.
The diaphragm should not be punched. 2. In new form of telephone in No
20, current volume, must there be a battery in the circuit, or is the
telephone sufficient to work it? A. A battery is required.
(42) J. M. B. asks: What will prevent the hair from falling out? A.
Keep the pores of the skin open by frequent bathing and change of
underclothing. Bathe the head with clean soft water, and stimulate
the scalp with a moderately stiff brush morning and evening. The head
should be occasionally cleansed with a weak solution of glycerin soap
in dilute spirit of wine, with care to remove all traces of soap from
the hair. Use no pomades or oils of any kind.
(43) B. H. P. asks (1) how to make malleable iron, such as used in
wrenches. A. Malleable iron castings are made from mottled iron. They
are cleaned by tumbling and then packed in iron boxes with alternating
layers of rolling mill scale. The boxes are carefully luted and packed
in an annealing furnace, where they are kept at a white heat for a
week or more, and then allowed to cool gradually. 2. How is steel
or iron made to adhere to the face of the jaws of the wrench? A. By
welding.
(44) J. G. E. asks: What is the highest column of water that can
be raised from a well by means of a siphon pump with 60 lbs. steam,
likewise a 1 inch column of water with 60 lbs. steam? A. Lift, from 26
to 27 feet.
(45) W. H. W. asks: 1. Is there any solution excepting rubber that
will make cloth thoroughly waterproof, or at least withstand the
attack of water for an hour or so? It should be applied by dipping
the cloth in the solution. A. Linseed oil boiled with a little wax and
litharge is useful for some purposes. Cloth prepared with paraffin,
balata gum, the gum of the asclet pias or milkweed, naphtha solution
of the dried pulp of the bamboo berry, anhydrous aluminum soaps (see
pp. 149 and 159, "Science Record," 1874), are also employed. 2. Is
there any chemical that could be combined with the solution, imparting
some property to the same for which rats or mice would have an
antipathy so as to prevent their attacks? A. A trace of phenol will
generally suffice.
(46) J. L. asks: Is the balata gum softened by animal oils or fat? A.
Yes.
(47) P. L. W. asks. What distance would a 100 lb. weight have to fall
to run a sewing machine for 5 hours? A. For an ordinary family sewing
machine, requiring about one thirtieth of a horse power, the weight
would have to fall about 3,300 feet in the 5 hours.
(48) W. G. R. asks: 1. What is the valve yoke of a steam engine? A.
We presume you refer to the rectangular yoke that receives the back
of the valve in the class of engines having balanced valves. 2. What
should be the diameter of the bore of an engine of 1 horse power with
100 lbs. pressure, also the length of stroke? A. Diameter, 23/4 inches;
stroke, 41/2 inches. 3. How are the back gears of a lathe made so as
to be thrown out of gear when it is wished to use the lathe at a high
speed? A. Ordinarily by a cam and lever, or tight and loose joint. 4.
Would 1/64 of an inch thickness of sheet steel be strong enough for
the boiler of a small model locomotive? How much pressure would it
stand to the inch? A. If the diameter does not exceed 3 inches, you
can carry a pressure of from 50 to 60 lbs. per square inch.
(49) J. W. W. asks: Which will stand the most pressure, a piece of
round iron 1 inch long and 1 inch in diameter, or a piece of gas pipe
the same dimensions, both being set upon end? A. The round iron.
(50) W. M. B. writes: 1. I have one eighth inch basswood, cherry,
butternut and walnut. Which do you advise for the sounding board of a
microphone and Hughes telephone? A. Either will do, but pine or spruce
is better. 2. Would a glazed earthen jar do for the outside of battery
described in SCIENTIFIC AMERICAN SUPPLEMENT, No. 149? A. Yes. 3. Could
I make insulated wire myself? If so, how? A. Wire may be insulated by
giving it a coat of shellac varnish and allowing it to become dry and
nearly hard before winding.
(51) W. H. S. asks how to satin finish tubing like sample sent. A. The
specimen has been electro-plated with silver in the usual manner,
and the electric current then reversed for a few moments, thus
redissolving a portion of the plate, the remainder presenting the
peculiar satin like luster.
(52) S. W. C. asks: Has carbon for telephone purposes ever been made
by subjecting the black deposited by a flame to a heavy pressure? A.
Yes. Edison's carbons are made in this manner.
(53) "Hardware" asks: 1. Where is best to take hot air in a room, at
register near ceiling or in floor? A. At or near the floor. 2. Where
is best place to have ventilation, near floor or near ceiling? A.
If connected with a flue having a good draught it should be near the
floor.
(54) R. W. J. asks: What causes the cracking noise in the pipes of a
steam heating apparatus, when a fire has been started to warm up the
building? Is it the water in the pipes made by condensed steam, or is
it the expansion of the pipes from being heated? A. The noise is due
to both causes in some degree, but principally to the water, which
produces violent blows.
(55) C. N. A. asks how to temper steel tools for working on stone or
similar work. There is some preparation which is put in water which
accomplishes the purpose when the steel is heated and plunged in. A.
Heat the tools to a cherry red, and plunge in clean, moderately cool
water. A little common salt is sometimes added to the water.
(56) G. B. asks: 1. Is the height to which water is raised by a
hydraulic ram measured from the ram itself or from the spring from
which the supply comes? A. From the ram. 2. Can a hydraulic ram be
constructed to discharge 1,000 gallons of water per minute? A. Yes.
(57) L. D. writes that benzine will answer much better to exterminate
roaches, moths, etc., than anything else. It will not hurt furniture
in the least, will evaporate, and can be easily applied.
MINERALS, ETC.--Specimens have been received from the following
correspondents, and examined, with the results stated:
M. B. W.--No. 1 is a silicious clay--it might be useful in the
manufacture of some grades of pottery, etc. No. 2 is a ferruginous
shale--contains about 80 per cent. of silica and 10 per cent. of
alumina, besides lime, magnesia, iron oxide, and water.--W. S.--It is
fibrous talc--talc of good quality is in considerable demand for paper
making and other purposes.--W. G. H.--The sand contains no precious
metal--the glittering particles are mica.--S. F.--The specimen you
send consists of a mass of the long hairs which have been attached
to the seeds of the "milkweed" (_asclepias_), or, as it is sometimes
called, from the silky nature of these appendages, "silkweed." We
believe that this material is put to no other economic use at present
than that of a filling for cushions and pillows. The beauty of this
silk like down long ago attracted attention, and many unsuccessful
attempts have been made to put it to some practical use in the arts;
but, as you have probably noticed, the hairs are both brittle and
weak, and an examination with a lens will show that it wants the
roughness and angularity necessary to fit it for being spun like other
fibers. It has, however, been mixed with cotton and woven into fabrics
having a silky luster and capable of taking brilliant dyes, but the
manufacture has never been prosecuted. The plants, though widely
distributed over the United States, and quite common, are nevertheless
not abundant enough in a wild state to afford much of a supply, and we
believe no experiments have been made in cultivating them.
* * * * *
Any numbers of the SCIENTIFIC AMERICAN SUPPLEMENT referred to in these
columns may be had at this office. Price 10 cents each.
* * * * *
COMMUNICATIONS RECEIVED.
The Editor of the SCIENTIFIC AMERICAN acknowledges with much pleasure
the receipt of original papers and contributions on the following
subjects:
Manufacture of Porous Cups for Tyndall Grove Battery. By W. H. S.
Cylinder Condensation. By F. F. H.
Sawdust. By W. H. M.
Keely Motor. By G. R. S.
Firing. By A. P. A.
Steam Launches. By G. F. S.
* * * * *
HINTS TO CORRESPONDENTS.
We renew our request that correspondents, in referring to former
answers or articles, will be kind enough to name the date of the paper
and the page, or the number of the question.
Many of our correspondents make inquiries which cannot properly be
answered in these columns. Such inquiries, if signed by initials only,
are liable to be cast into the waste basket.
Persons desiring special information which is purely of a personal
character, and not of general interest, should remit from $1 to $5,
according to the subject, as we cannot be expected to spend time and
labor to obtain such information without remuneration.
* * * * *
English Patents Issued to Americans. From November 8 to November 12,
inclusive. Electric light.--T. A. Edison, Menlo Park, N. J. Feed water
apparatus.--S. J. Hayes et al.,-------.
Pipe, manufacture of.--W. Radde, N. Y. city.
Potato digger.--L. A. Aspinwall, Albany, N. Y.
Refrigerator.--J. A. Whitney, N. Y. city.
Screw cutting machinery.--C. D. Rogers, Providence, R. I.
Sewing machine.--Wilson Sewing Machine Company, Chicago, Ill.
Wire machinery.--C. D. Rogers, Providence, R. I.
* * * * *
[OFFICIAL.]
INDEX OF INVENTIONS
FOR WHICH
Letters Patent of the United States were
Granted in the Week Ending
October 15, 1878,
AND EACH BEARING THAT DATE.
[Those marked (r) are reissued patents.]
* * * * *
A complete copy of any patent in the annexed list, including both the
specifications and drawings, will be furnished from this office for
one dollar. In ordering, please state the number and date of the
patent desired, and remit to Munn & Co., 37 Park Row, New York city.
* * * * *