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inquirers.
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.
Correspondents whose inquiries do not appear after a reasonable time
should repeat them. If not then published, they may conclude that,
for good reasons, the Editor declines them.
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.
Any numbers of the Scientific American Supplement referred to in
these columns may be had at this office. Price 10 cents each.
* * * * *
(1) L. L. asks: 1. How can I grind and polish quartz and agate rock,
and what kind of grinding and polishing material should I use? A.
Quartz and agate are slit with a thin iron disk supplied with
diamond dust moistened with brick oil. The rough grinding is done on
a lead wheel supplied with coarse emery and water. The smoothing is
done with a lead lap and fine emery, and the polishing may be
accomplished by means of a lead lap, whose surface is hacked and
supplied with rottenstone and water. 2. What is the best method of
polishing steel? A. The usual method is to grind first on a coarse
wet stone, then on a fine wet stone, then on a lead lap supplied
with fine emery and oil, and finally polish on a buff wheel supplied
with dry crocus and revolving rather slowly.
(2) R. L. J. asks how to make copying black and red inks. A. 1.
Bruised Aleppo nutgalls, 2 lb.; water, 1 gallon; boil in a copper
vessel for an hour, adding water to make up for that lost by
evaporation; strain and again boil the galls with a gallon of water
and strain; mix the liquors, and add immediately 10 oz. of copperas
in coarse powder and 8 oz. of gum arabic; agitate until solution of
these latter is effected, add a few drops of solution of potassium
permanganate, strain through a piece of hair cloth, and after
permitting to settle, bottle. The addition of a little extract of
logwood will render the ink blacker when first written with. Half an
ounce of sugar to the gallon will render it a good copying ink. 2.
Shellac, 4 oz.; borax, 2 oz.; water, 1 quart; boil till dissolved,
and add 2 oz. of gum arabic dissolved in a little hot water; boil
and add enough of a well triturated mixture of equal parts indigo
and lampblack to produce the proper color; after standing several
hours draw off and bottle. 3. Half a drachm of powdered drop lake
and 18 grains of powdered gum arabic dissolved in 3 oz. of ammonia
water constitute one of the finest red or carmine inks.
(3) X. inquires: What is the rule for making a counterbalanced face
wheel for engines? A. It is a common practice to place the counter
weight directly opposite the crank, with its center of gravity at
the same distance from the center of the shaft as the center of the
crank pin, making its weight equal to weight of piston, piston rod,
crosshead, and crank pin, plus half the weight of the connecting
rod.
(4) A. R. asks: What is the best way to remove cinders from the eye?
A. A small camel's hair brush dipped in water and passed over the
ball of the eye on raising the lid. The operation requires no skill,
takes but a moment, and instantly removes any cinder or particle of
dust or dirt without inflaming the eye.
(5) D. F. H. asks: Can I move a piston in a half inch glass tube by
the expansion of mercury? A. Yes, but you will require a long tube
to get any appreciable motion of the piston.
(6) J. W. asks: What size of a bore and what length of a stroke I
would want for a rocking valve engine of half a horse power? A.
About 2 inches cylinder and 3 inch stroke, depending upon pressure
and velocity.
(7) R. W. H. writes: In a recent discussion on hot air and steam
portable engines it was decided to ask your opinion, which should be
final. Water is scarce, though enough to use steam is easily procured.
The country is hilly, so that lightness is desirable. The power wanted
is 6 horse, and movable, that is, on wheels. Which will be best, hot air
engine or steam engine? Which consumes most coal for a given power?
Which will be cheapest in above case? A. For small powers the hot air
engine is most economical, but we do not think it adapted to your
purpose. We would recommend the steam engine for a portable power.
(8) J. C. T. writes: 1. I have a water tank for supplying my boiler,
which is made of No. 22 galvanized iron; size 30 inches by 9 feet 4
inches. How many gallons will it hold? A. 342 gallons. 2. Will it be
better to have it painted inside? A. Yes. 3. How many years will the
tank wear under favorable circumstances, using well water? A.
Depends upon the care taken of it.
(9) W. H. C. asks: Is there any way of deadening the noise of machinery
overhead from the engine room below? The noise comes from machinery in
the weave room of an alpaca mill. A. This is generally accomplished by
setting the legs of the machines on thick pieces of India-rubber or
other non-conductor of sound.
(10) G. H. asks: How can I mount photos on glass and color them? A.
Take a strongly printed photograph on paper, and saturate it from the
back with a rag dipped in castor oil. Carefully rub off all excess from
the surface after obtaining thorough transparency. Take a piece of glass
an inch larger all round than the print, pour upon it dilute gelatin,
and then "squeegee" the print and glass together. Allow it to dry, and
then work in artists' oil colors from the back until you get the proper
effect from the front. Both landscapes and portraits can be effectively
colored by the above method without any great skill being required.
(11) C. W. S. asks: 1. Is there any practical and effective method known
for cutting screws by connecting the slide rest with the mandrel of the
lathe by gears or otherwise? A. This can be done in this way: attach a
spur wheel to the back of the face plate. Mount a similar wheel on a
short hollow shaft, and support the shaft by an arm bolted to the lathe
bed so that the two spur wheels will mesh together. Fit right and left
hand leading screws to the hollow shaft of the second spur wheel, and
drill a hole through them as well as through the hollow shaft to receive
the fastening pin. Now remove the longitudinal feed screw of the slide
rest and attach to one side of the carriage an adjustable socket for
receiving nuts filled to the leading screws. The number of leading
screws required will depend of course on the variety of threads it is
desired to cut unless a change of gear is provided. 2. A writer in a
foreign journal claims to make slides, or V-shaped pieces for slide
rests, eccentric chucks, etc., on his lathe. Is any such process known
here, or any process within the capabilities of an amateur mechanic by
which the planing machine can be dispensed with? A. For small work held
between the lathe centers a milling device fitted to the slide rest in
place of the tool post will answer an excellent purpose. This device
consists of a mandrel carrying at one end the cutter and at the other
end a large pulley. This mandrel is journaled in a hinged frame
supported by a block replacing the tool post, and is adjusted as to
height by a screw passing through an arm projecting from the supporting
block. The direction of the belt is adapted to this device by means of
pulleys.
(12) J. E. B. asks: 1. What is the best turbine water wheel now in use?
A. There are several wheels in market that seem equally good. You should
examine all of them and decide from your own observation which is best.
2. What is the rule for finding the horse power of water acting through
a turbine wheel which utilizes 80 per cent of the water? A. Finding the
weight of water falling over the dam and its velocity in feet per
minute, multiply the weight in pounds by the velocity, and the result is
foot pounds, divided by 33,000, the quotient is theoretical horse power;
if your wheel gives out 80 per cent. then 80 per cent of that result is
the horse power of the wheel. 3. How can I calculate the capacity of a
belt? A. You will find an exhaustive article on the subject of belts on
pp. 101, 102, Vol. 42, Scientific American, which contains the
information you desire. 4. What machine now in use is the best, all
things considered, for the manufacture of ground wood pulp? Where are
they manufactured? A. This information can probably be obtained by
inserting an advertisement in the Business and Personal column of this
paper.
(13) C. A. R writes: Wishing to renew my Leclanche batteries, which were
giving out, I bought some new empty porous cells. Please give the
following information: 1. Can I use the carbon plates of the old
elements over again? If so, do they need to undergo any washing or
soaking; or are they as good as ever? A. Yes. Soak them for a few hours
in warm water. 2. Is there anything I must add to the granular manganese
with which I fill the cells, in order to obtain maximum power and
endurance? Some makers add pulverized or even coarsely broken carbon. Is
it an advantage? A. It is an advantage to add granulated carbon to the
manganese. Use equal parts of each. 3. What is the exact composition of
the curdy mass which forms around and especially underneath the zincs of
newly mounted and old gravity batteries. Is this substance formed
naturally, or is it the result of using poor zinc or sulphate of copper?
A. It is copper, and should be removed, for it weakens the battery. It
is the result of placing the zinc in the sulphate of copper solution. 4.
Is there any real advantage in amalgamating the zincs of the above
batteries? A. No. 5. Is there a speedy way of cleaning them when coated
with this substance? A. They can be cleaned by scraping. 6. At certain
occasions my electric bells began ringing without anybody apparently
closing the circuit. I often notice that if I unjoin the batteries and
let them remain thus for a few hours, on reconnecting them the bells
would work all right for a week, sometimes a fortnight, when the same
trouble would again occur. Can you in any way explain this phenomenon?
The batteries are not placed in a very dry part of the house, but the
wires, which run pretty closely together, are nearly all exposed, so
that I can control the slightest corrosion or uncovering of the
conductors. A. There must be some accidental closing of the circuit. We
could not explain the action of your line without seeing it.
(14) J. E. E. asks: What is the number of layers of wire, and the size
used for the primary of the induction coil in the Blake transmitter, and
as near as you can the amount used for secondary? A. For primary, use
three layers of No. 20 magnet wire, and for the secondary use twelve or
fourteen layers of No. 36 silk covered copper wire. The resistance of
the secondary wire should be from 100 to 150 ohms.
(15) J. M. I. asks how to make a barometer by coloring ribbon, so that
they will change color, indicating weather changes. A. Use a moderately
strong solution of chloride of cobalt in water.
(16) O. C. H. writes: In reply to R. A. R., question 22, in Scientific
American, December 4, I will say that some months ago I was engaged in
running a saw mill, lathe, and shingle factory; was troubled with two
hot boxes, and frequently had to stop and apply ice. Seeing in the
Scientific American a reference to the use of plumbago, I sent for some,
and after three or four applications was troubled no more with hot
boxes.
(17) F. W. asks: What is the best way for return pipe to go into the
boiler from radiators--steam at 60 lb. per square inch, fall 15 feet? A.
If your job is properly piped you can bring your return pipe in at any
convenient place in your boiler below the water line. If you go into the
feed pipe, have your connection inside all other valves.
(18) L. T. G. writes: 1. I have four cells of carbon battery; the
solutions are bichromate of potash and sulphuric acid. Also three cells
of the Smee; sulphuric acid one part, to ten of water; and the four
cells of the carbon battery are not sufficient to run my small
electro-magnetic engine, for more than two or three minutes. I wish to
know if it would be injurious to either one of the batteries if I should
unite them both in one circuit, to run the engine, for about one or two
hours at a time. A. The batteries will not be injured, but they will not
work well together. Better increase the number of carbon elements. 2.
Will either of the above batteries freeze in winter, or will cold
weather affect their working? A. They will not freeze, but it is better
to keep them at a temperature above freezing 3. Is it always best to use
the largest wire in connecting batteries with any instrument, say, above
No. 11 or No. 12 wire, as the larger the wire the less the resistance,
thereby getting nearly the full power of the battery? A. Yes. 4. What
purposes are quantity and intensity electricity best suited for
respectively? A. Batteries are arranged for quantity or intensity
according to the work to be done. The maximum effect is obtained when
the battery elements are combined, so that the total resistance in the
elements is equal to the resistance of the rest of the circuit.
(19) J. H. asks: Which would be the strongest, two 2-inch by 4-inch
joists nailed together, or one 4-inch by 4-inch joist? A. One 4-inch by
4-inch.
(20) J. K. B. writes: I suppose every experimenter who uses a carbon
battery has been troubled by the uncertainty of the carbon connection.
The makers of the Grenet battery seem to have solved the problem. Can
you tell us through your correspondence column what solder they use, and
how they make it stick? A. The carbon is coated with copper by
electro-deposition; this coating is readily soldered to the carbon
support with common soft solder.
(21) M. D. M. asks: 1. Is there a difference in a steam engine between
the boiler pressure and the pressure on the piston when the piston is
moving 460 feet per minute? A. Yes. 2. About what difference? A. From 2
to 8 lb., depending upon size and length of steam pipe. 3. Does the
difference between them vary with a difference in the motion of the
piston in the same engine? A. Not appreciably within usual limits of
speed.
(22) F. writes: We have just closed up our steam stone works for this
season, and we wish to know what is best to coat the inside of our steam
boilers to keep them from rusting. Some say black oil, and others common
tallow: which do you recommend as the best? A. We think the black oil
quite as good and cheaper than tallow. Have the surfaces thoroughly
cleaned before applying the oil.
(23) O. H. asks for a cheap and easy way of amalgamating battery zincs.
A. It depends on the kind of battery. In the Fuller the mercury is
placed in the porous cell with the zinc. In bichromate batteries all
that is necessary is to dip the zinc in the bichromate solution and then
pour on a drop or two of mercury. It soon spreads over the entire
surface of the zinc. Another method is to dip the zincs in dilute
sulphuric acid and then pour on a little mercury, but these methods,
except in the case of the Fuller battery, are wasteful of mercury. It is
better to apply an amalgamating solution with a brush. This solution is
made by dissolving one part (by weight) of mercury in five parts of
nitro-muriatic acid (nitric acid one part, muriatic acid three parts),
heating the solution moderately to quicken the action; and, after
complete solution, add five parts more of nitro-muriatic acid.
(24) G. W. asks: 1. Would a perfectly round ball of the same specific
gravity throughout lie still on a level surface? A. Yes. 2. Can a
mechanic's square be made so true that a four-inch block may be made
exactly square by such an instrument? A. Yes.
(25) W. H. asks: 1. What is the weight of a boiler 24 feet long, 44
inches diameter, ¼ inch thick? A. With two flues, 16 inches diameter,
6,900 lb. 2. What is the contents (in gallons) of a tank 15 feet deep,
10 feet in diameter, top and bottom diameters being equal? Please give
me a formula. A. Area of 10 feet diameter = 78.54 x 15 feet deep = 1,178
cubic feet, and, allowing 7½ gallons per cubic foot = 1,178 x 7.5 =
8,835 gallons.
(26) C. L. W. writes: I have constructed a small induction coil to be
used for giving shocks. It is 3 inches long. The primary coil is wound
with 3 layers of No. 18 cotton covered wire, and the secondary consists
of about 12 layers of No. 38 silk covered. 1. How many cells and what
kind of battery shall I use to get the best results? A. For temporary
use one cell of Grenet battery would answer, but for continued use some
form of sulphate of copper battery is to be preferred. 2. Is it
necessary that the spring and screw in the interrupter should be coated
with platinum? A. Yes; otherwise they would soon burn out.
(27) H. C. P. writes: In the Scientific American of September 18, Mr. B.
Y. D., query 26, asks whether a sun dial, made for latitude 48° 15', can
be utilized in latitude 38° 50' for showing correct time. To make his
dial available in the lower latitudes, he has only to lift the south
side, so as to give the face a slope to the north, equal to the
difference of the latitude, in this case 9° 25'. For then the plane of
the gnomon being in the plane of the meridian, the edge of the gnomon
casting the shadow will be parallel with the earth's axis; and the face
of the dial will be parallel with the horizon of the latitude for which
the dial was made, and the graduation will show the time required; that
is, on the supposition that it was correctly made, and for a horizontal
dial.
(28) O. M. M. asks for a cheap process of plating steel case knives
with tin. A. Clean the metal thoroughly by boiling in strong potash
water, rinsing, pickling in dilute sulphuric acid, and scouring with a
stiff brush and fine sand. Pass through strong aqueous salammoniac
solution, then plunge in hot oil (palm or tallow). When thoroughly
heated remove and dip in a pot of fused tin (grain tin) covered with
tallow. When tinned, drain in oil pot and rub with a bunch of hemp.
Clean and polish in hot sawdust.
(29) V. R. P. writes: I have an aquarium which contains 4-2/3 gallons of
water. How many fish must I have in it--average length of fish 1½ to 2
inches to insure the health of the fish? At present, I refill the
aquarium semi-weekly. Please tell me a process by which I can lengthen
the time. A. Put in three fish, 1½ inches in length, to one gallon of
water, one small bunch of fresh water plants to one gallon of water.
Tadpoles (after they have cast their branchia or gills), newts, and rock
fish can be used to the extent of six to the gallon. The aquatic plants
will supply the fish with sufficient oxygen, so that the water will
seldom require changing.
(30) A. S. writes: I am about to construct an aqueduct 1,200 feet in
length, the water level differing 40 feet. By placing a forcing pump in
the valley I could then raise the water to a height of 40 feet, and
having erected a tank at that height and connected it by means of pipes
with another tank 1,200 feet distant, but on the same level, the water
according to a law of nature would travel over the distance of 1,200
feet. But finding it very difficult to erect tank 40 feet high, I would
prefer to construct the whole on the incline. Will the forcing pump
having just power enough to raise the water 40 feet perpendicularly into
the tank have sufficient power to force it into a tank of the same
elevation through 1,200 feet of pipe running on the incline, or must I
have more power, and how much more? A. The forcing pump must have enough
more power to overcome its own additional friction and the friction of
water in the long inclined pipe. Allow 20 per cent more power at least.
* * * * *
MINERALS, ETC.--Specimens have been received from the following
correspondents, and examined, with the results stated:
Box marked C. H. (no letter.)--1. and 2. Garnetiferous quartz rock. 3
and 4. Micaceous quartz rock. 5. Granite. 6. Basalt with traces of
chalcopyrite.--L. C. G.--They are fossil sharks' teeth, common in marl
beds.--J. E. C.--1. Iron sulphide and lead sulphide. 2. Quartzite, with
traces of galena and molybdic sulphide. 3 and 4. Dolomite. 5.
Fossiliferous argillaceous limestone, containing traces of lead
sulphide. 6. Lead sulphide in argillite.--C. T. M.--1. A silicious
kaolin. 2. Similar to No. 1. Useful if mixed with finer clay for white
ware. 3. Silicions carbonate of lime--some of this would probably make
fair cement. 4. Brick--the clay from which this was made would probably
be useful to potters. 5 and 6 are very silicious clays.
* * * * *