G.B., of Iowa.--Nominal horse power is merely a conventional expression for diameter of cylinder and length of stroke, and does not apply to the actual power of the engine. It is found by multiplying the cube root of the stroke in feet by the square of the diameter in inches and dividing the product by 47. This rule is based upon the postulate established by Watt, that the speed of a piston with two feet stroke is 160 feet per minute, and that for longer strokes the speed varies as the cube roots of the length of the stroke. It is needless to say this rule is not observed in modern practice, yet the expression, nominal horse power, is like many other relics of past time still retained. The above rule does not apply to high pressure engines. For such engines Bourne has given the following rule: Multiply the square of the diameter of the cylinder in inches by the cube root of the stroke in feet, and divide by 15.6.

The real power of an engine is estimated from the mean effective pressure in the cylinder--not the boiler--and the speed of the piston.

Your data are insufficient to determine the horse power of your boiler.

The horse power of boilers is estimated from the extent of heating surface when the grate and all other things are correctly proportioned, but with them as with engines, only actual test will positively determine it. The pipe you mention ought to be enlarged as proposed.

W.H.R., of Ma.s.s.--Pressure acts independently of the mode of application. A tun laid upon the head of a wedge would produce the same effect as though it were applied through toggles. When, however, a weight is dropped its effect increases as the square of its velocity.

J.B., of N.Y.--We recommend you to get "Appleton's Dictionary of Mechanics." Also send for descriptive catalogue to Henry Carey Baird, Philadelphia, from which you will be able to judge for yourself what works are suited to your requirements.

T.D.H., of Ma.s.s.--Ammonia, in a weak solution, may be used to cleanse the scalp, but is not recommended for the purpose. Borax in solution is better. The supposed preservation of the color of the hair by its use is a mistake.

F.B.H., of Ill.--So far as we know, nothing better than the flax seed bag has been discovered for packing the lower end of tubes in artesian wells. We have never heard of any trouble arising from the method and think you will have none.

L.G. of Ma.s.s.--Express the decimal ratio of the diameter of a circle to the circ.u.mference to which you refer, as a mixed vulgar fraction, and you will have what you ask for, if we understand your query.

A.H.S., of Sandwich Islands.--We know of no substance that in our opinion, could be used advantageously to paint the interior of sheet-iron evaporating pans for concentrating cane juice.

L.B., of Wis.--We would be glad to a.s.sist you but the data you furnish are not sufficient. The accurate solution of such a problem involves the higher mathematics.

A.H.M.--All animal and mineral oils are destructive to rubber. Linseed oil will not dissolve it. Oils should not be allowed to get on rubber belting.

T.W.J., of Pa.--For your rollers try some emery mixed in a solution of gum sh.e.l.lac in good alcohol.

E.B., of Ma.s.s.--The patent can be corrected by reissue.

J.M.T., of Ind.--To find the proper area for a safety valve port, when the evaporating surface is properly proportioned to the engine power, multiply the square of the diameter of the piston in inches by the speed in feet of the piston per minute, and divide the product by 375 times the pressure on the boiler per square inch. Having decided upon the length of the lever, the distance of the valve stem from the fulcrum, and the point from which the weight will be suspended, the weight necessary will be found by multiplying the area of the valve port in inches into the pressure per square inch in the boiler in pounds, and this product into the distance of the center of the valve stem from the fulcrum in inches, and dividing the product thus obtained by the distance from the fulcrum to the point of suspension of the weight in inches. The quotient will give the weight in pounds.

A.K.S., of Ohio.--The inclination of the poles of a planet to the plane of its...o...b..t, determines its zones and also its seasons. The inclination of the earth's axis is twenty-three and one half degrees. This places the tropics the same distance each side of the equator, and the polar circles the same distance from the poles. The torrid zone is therefore forty-seven degrees wide, and the temperate zones each forty-three degrees wide. As the planets vary in their inclination of their axis to the planes of their orbits, it follows that their zones and seasons differ from those of the earth.

W.H.C., of Texas.--The teeth of a circular wood saw to be driven by foot-power, should be not larger than those of the ordinary hand crosscut. The fly-wheel ought to have a rim weighing from eighty to one hundred pounds, and it should be, for a 12-inch saw, not less than a foot in diameter. It should be placed on the saw arbor. The belt should not run on the fly-wheel, but on a special pulley, and the treadle and crank motion should be so adjusted that the foot will move through an arc of from 10 to 12 inches.

A.H.B., of Pa.--We advise you to use a battery in coating the small gray castings, of which you write, with copper. It will be all the more satisfactory in the end. The best polishing material to put in with them in the tumbler we think would be leather cuttings and sweepings.

They will not need returning to the tumbler after being coppered.

We recommend you to get "Byrne's Practical Metalworkers a.s.sistant,"

published by Henry Carey Baird, Philadelphia.

J.H.G., of Tenn.--Don't put oil in your boiler to prevent incrustation.

It will not probably do any good, and it will cause much foaming, while besides that it is a waste of heat, it is injurious to engines.

S.S.R., of Tenn.--No ammoniacal engines are, so far as we are aware, running in this country.

C.E.C., of Ohio.--The varnish for patterns is common sh.e.l.lac varnish. It is sometimes made black by lampblack.

RECENT AMERICAN AND FOREIGN PATENTS.

_Under this heading we shall publish weekly notes of some of the more prominent home and foreign patents_.

MOP.--Philip Cook, Jr., Sioux City, Iowa.--This invention relates to a new and useful improvement in mops, whereby they are so arranged that they may be wrung or freed from water when in use by moving the slides connected with the handle and head of the mop.

VENTILATING HORSE COVER.--Charles P. Eager, Boston., Ma.s.s.--This invention relates to a new horse cover, which is so arranged that it will be entirely waterproof, and nevertheless permit a free escape of air from the body of the animal.

CAR COUPLING.--S.O. Campbell, Tipton, Mo.--This invention relates to a new car coupling, which is so arranged that it will be self-coupling and retain the coupling pin ready to lock as long as the link is not inserted.

GAS STOVE.--Wm. J. Hays, New York city.--This invention has for its object to construct a gas stove, with an extender radiating surface, and with proper air channels, so that with a comparatively small amount of heat, the air in an ordinary-sized room can be properly warmed.

SCRIBE HOOK FOR WEATHER BOARDING.--John Nester, Portland, Oregon.--This invention relates to a new scribe hook for weather-boards, which will be generally useful and adaptable to the purposes for which it is intended and to provide an adjustable spur and marker.

RAILROAD SMOKE CONVEYER.--Lemuel Powell, Milford, Conn.--The object of this invention is to prevent the smoke and ashes, issuing from the smoke stack of a locomotive, from entering the cars of the train and from thereby preventing the proper ventilation of the cars.

DRILL FOR BORING POLYGONAL HOLES.--J.C. Broadley, Franklin, N.J.--This invention relates to a new implement for boring polygonal, oval, star-shaped, or holes of other suitable form, in metal, wood, or other material. The invention consists chiefly in arranging the pattern, which regulates the shape of the hole to be bored, on the upper part of the drill shank, and in having the bit shanks, which are pivoted to the lower part of the drill shank, held by means of springs against the inner edges of the inverted cup-shaped pattern.

ROOFING.--H.G. n.o.ble, Selma, Ala.--This invention relates to improvements in roofing, and consists in covering roofs with sheet metal, laid on the rafters and nailed down at the edges, so as to be considerably concaved between them, the joints on the rafters being covered by inverted caps or troughs. The concave form of the sheet is designed to prevent the sheet metal from cracking, to which it is subject by expansion and contraction when laid on flat.

WASHING MACHINE.--John J. Kimball Naperville, Ill.--This invention relates to improvements in washing machines, and consists in an improved arrangement of operating mechanism for revolving a vertically suspended shaft with a crank at the top, and carrying within the tub a corrugated or roughened rubber, for action on the clothes. The invention also comprises an improved arrangement of the rubber, whereby it is made capable of sliding up or down on the shaft, according to the amount of clothes to be acted on.

BOLT CUTTER.--O.E. Butler and S.P. Dunham Marshalltown, Iowa.--This invention relates to improvements in hand instruments for cutting bolts, and consists in the combination with the handles of an instrument, such as patented to the inventors, January 19, 1869, as an improved instrument for sharpening horseshoes, of a cutting pin of peculiar construction, whereby the said tool is adapted, when this cutter is applied in subst.i.tution of the cutter and jaw, is used for sharpening horseshoes, to cut off the ends of bolts with great facility.

SHAFT TUG LUGS FOR HARNESS.--T.J. Magruder, Marion, Ohio.--This invention relates to improvements in the construction and application of shaft tug lugs for harness, and consists in forming the said lugs with broad and long plates, properly curved to suit the curve of the pad, and connecting the latter to the under sides of the skirts and to the pads in a way to stiffen the skirt and to hold the stud securely from breaking loose, the said lugs being made solid with a screw nut at the end to confine the bearing straps, or hollow, with female screw threads near the base, and bolts s.c.r.e.w.i.n.g into the said female threads to secure the bearing straps and to admit of readily applying or removing the straps so that the harness may be adapted for use either as single or double harness.

HARNESS BUCKLE.--J.W. Burch, Fayette, Miss.--The object of this invention is to provide buckles for harness and other uses, with tongues constructed in the form of leather punches, whereby they may be used at any time required for punching holes.

HUMMING-WHEEL TOY.--A.F. Able, New Orleans, La.--This invention relates to improvements in humming wheel toys, having for its object to provide an improved holding apparatus for supporting and maintaining the proper tension on the cords, and designed to support the cords of two or more wheels at the same time.

COMBINED CLOTHES IRONING TABLE AND CLOTHES DRYER.--William P. Adams, Brooklyn, N.Y.--This invention relates to a new and useful improvement in an article for the laundry, and consists in an adjustable ironing table, and in combination therewith a clothes dryer.

SEED AND GRAIN STRIPPER.--J.F. King and H.A. Rice, Louisiana, Mo.--The object of this invention is to provide a seed and grain stripper, with light and strong fingers, capable of adjustment as to hight, and arranged in a way to vary the s.p.a.ces between the teeth at the point of stripping the heads for straw of different sizes.

CLOTHES WRINGER.--M.M. Follett, Lake City, Minn.--This invention relates to a new apparatus for applying pressure to the rollers of a wringer with an object of obtaining equal and adjustable power without any danger to the rubber of the rollers or to the articles to be dried.

AUGER HANDLE.--James Swan, Seymour, Conn.--The object of this invention is to provide a cheap, simple, and durable handle for augurs for boring in wood, one which shall require no fitting except to make the augur enter the socket, and which shall be of such size and shape that the shanks of ordinary augurs shall enter without any fitting at all.

CANDLESTICK.--H. Zahn, San Francisco, Cal.--This invention relates to a new and useful improvement in candlesticks, and consists in the use of a thumb screw in combination with the candlestick tube, whereby the candle is kept steady, and in a perpendicular position in the stick, and firmly held without the use of springs or other attachment.

WASHING MACHINE.--J.S. Merchant, Hopedale, Ohio.--This invention relates to new and useful improvements in machines for washing clothes.

PACKING CASES FOR OIL CANS.--John McLeod Murphy, New York city.--This invention consists of an arrangement especially adapted for use with cans provided with an improved cut off nozzle, which is the subject of an application for a patent, made by the same inventor and bearing even date herewith, which said improvement comprises the application to the ordinary vertical nozzles of a lateral spout connected to the side, and arranged to open an escape pa.s.sage for the contents when the said spout is turned with the right position, which position is that best adapted for pouring from the can into another vessel, and in which the said spout projects through a slot in the side of the packing case in closing it, the said case being provided with an opening and a door for closing the same adapted for it.

WASHING MACHINE.--Edward Heim, Pittsburgh, Pa.--This invention relates to a new machine for washing clothes, and consists in the introduction of several improvements whereby the machine is adapted to thoroughly clean coa.r.s.e as well as fine articles without injury to the same, and in a comparatively short time.

PADLOCK--John S. Rankin, Ann Arbor, Mich.--The object of this invention is to provide a simple, cheap, and efficient construction and arrangement of the locking and operating parts of padlocks. The invention consists in an improved and simple compound tumbler bolt and relative arrangement thereof with the bow and bow spring.