wooden blocks. By this arrangement contact between the hand and the rubber is avoided. Some people let their erasing rubber get very dirty, and then express suprise that it fails to clean paper.

curved or cylindrical bodies, this being illustrated case of cotton or linen goods, a composition of the
by rocket cases printed under Mr. Leighton's di- following nature may be spread on the fabric:
rections 12 years since. Much ingenuity is dis- 201b. washed rubber, 20lb. zinc white, 5lb. sul-
played in the construction of the various self-ink-phur, 6lb. or 9lb. of solvent naphtha. When, on the
ing pocket and pencil stamps. These are before
you, and you can examine them for yourselves.
I, for one, believe that the time will come when
newspapers and books will be largely printed
from india-rubber stereotypes. They can be
easily and rapidly made, and I have cured rub-
ber very successfully in the usual paper or

Very pretty casts or moulding of phototypic reliefs can be made in vulcanized india-rubber; and I will next illustrate to you the method of making such casts, at least as far as the manipulation af the caoutchouc is concerned. Here is an ordinary photographic negative, and this is a type-metal cast or mould, produced by photo-"flong" moulds, faced with tin or lead foil, this graphic agencies from the negative. Those portions of the negative which are opaque correspond to relief in the type-metal mould, while the depressions of the mould correspond with the transparent portions of the negative.

The first step is to very slightly oil the mould, after which black-lead is applied to the surface, and the excess is polished off by means of a soft brush. A sheet of mixed rubber, previously softened by heat, is next applied to the prepared surface of the mould, and curing is effected by means of the small hot press into which the mould and rubber are now placed. A hot press of the kind now before you (Fig. 16) is very convenient for the curing of small flat articles and casts. It consists of a cast-iron fish-kettle, upon the bottom of which rests a slab of type metal an inch thick. Inside the kettle is placed a small press, like a copying press in miniature. By the side of the press stands a small iron cup, containing glycerine, and in this fluid is immersed the bulb of a thermometer, the stem of which projects through a hole in the cover of the kettle. By means of a small gas stove heat can be applied to the apparatus, and it is easy to so adjust the gas supply that the thermometer shall indicate a tolerably constant temperature of, say, 140° or 150° Centigrade. Most qualities of mixed rubber will become fairly well cured by being heated under these circumstances for half to one hour, and any tendency towards adhesion to the mould is obviated by the preparation with oil and blacklead, as described.

This apparatus is extremely well adapted for curing the india-rubber stereotypes or stamps which are now so extensively used for endorsement and other purposes. To make these stereotypes a reverse or mould is made from the types, this being taken in plaster-of-paris, or, better B

latter being laid first on the type. The steam
press (Fig. 16) might be employed for curing a
rubber stereotype much larger than anything yet
attempted in metal; and by employing a suitable
rubber composition it is not unlikely that a
thorough curing might be effected in as short a
time as ten or fifteen minutes. The power re-
quired to drive printing machines working with
rubber stereotypes would be comparatively small,
while impressions quite as sharp as those from
metal ought to be secured. One advantage in
the rubber stereotypes would be the ease with
which they can be adapted to cylinders of any
curvature. As regards ink for stereotypes a few
words may be said. A fatty ink naturally in-
jures the rubber—at any rate if it is not very care-
fully removed after use; but an ink having
glycerine as a basis answers extremely well, and
may, as the specimens on the table prove, be left
in contact with the stamps without in any way in-
juring them.

other hand, the curing is to be performed by the cold process, the sulphur may be omitted. After the rubber has been softened by the absorption of the solvent naphtha, the materials are thoroughly incorporated by means of a mixing or kneading machine.

A very good illustration of the action of a spreading machine is afforded by the model which is now before you. It (Fig. 17) consists of a baseboard A, over which is supported a rule-like bar B.

steam chest in order to dry off the solvent naphtha. In the case of ordinary goods about six coats are given-three in each direction. Each coat may be estimated as being about one hun dredth of an inch in thickness.

The method of applying the mixture of carbon disulphide and chloride of sulphur used for effecting the cold vulcanization of the india-rubber coating, when spread on goods which would be injured by high-pressure steam, is of some interest. The coated fabric C (Fig. 18) passes round a roller D, the coated side being outwards, and at the point E it is brought into contact with a more rapidly revolving slate roller A, which dips in the vulcanizing solution, this being contained in a trough B. The solution, which consists of 1 part of chloride of sulphur and 40 parts of carbon disulphide, is led upwards by the roller A towards the point E, where it forms a kind of accumulation or wave. All excess drains back as the fabric travels towards the point C.

Inking rollers made of india-rubber have been occasionally made use of from time to time for many years, but owing to inexperience in their manufacture and use the results have been, until The material to be coated is placed under the quite recently, far from satisfactory. You will bar, a quantity of the paste or dough is piled up probably remember that when lecturing here on in front of the bar at C, and the cloth is drawn photo-mechanical printing I showed you how forward towards D, so that the rule or bar cuts a printing roller could be made with a body of the off an even layer of the soft mixture. In actuausual soft gelatine composition and a face of red practice the fabric, after having received a coatvulcanized rubber, smoothed by means of glassing of the composition, is passed over a heated paper. This circumstance brought to my knowledge the fact that Mr. Robert Lanham had been very successfully laboring in the improvement of india-rubber rollers. By the kindness of Mr. Lanham I was enabled to show you some of his rollers at the lecture immediately following the occasion when I showed you my own. During the two years which have elapsed since that time Mr. Lanham has still further developed the manufacture of rubber rollers for printing purposes, and I am indebted to him for the opportunity of now showing you the very fine collection of these articles which stand over yonder. Mr. Lanham makes his rollers from red rubber, which is, of necessity, very thoroughly cured, in order to enable it to withstand the action of fatty inks; and after the rollers have been turned true by still, in metal. When plaster is employed it is means of self-acting lathes a fine surface is given well to harden it by saturating it with an alcoholic to the rubber by means of glass-paper. In order solution of shellac, and again drying. The soft to give his rollers the softness which is necessary mixed rubber is then forced into the mould, as in some cases Mr. Lanham now introduces a you now see me doing it, after which the curing series of perforations parallel to the axis. For may be effected in the hot press (Fig. 16). lithographic printing these rollers have very conMr. John Leighton introduced rubber stereo-siderable advantages over the usual leather roller, types about 18 years ago, and since that time their use has become very general for a great variety of purposes. Mr. Leighton has very kindly sent for your inspection an interesting collection of specimens illustrative of the manifold uses to which india-rubber stereotypes can be applied. Glass and other hard bodies may be printed on with the greatest ease; and by dusting the impression with a vitrifiable color the impressions may be burnt in. Here are some of Mr. Leighton's specimens, illustrating what was done in this direction as far back as 10 years ago. Again, the rubber stamps lend themselves ad

A

FIG. 17.

and some excellent samples of work done with
them hang on the walls.

India-rubber does many services in connection
with the art of printing, some of these being of
very great interest, but it is impossible to go
farther into the matter this evening.

Waterproof goods, consisting of a thin layer of rubber spread on a textile fabric, are very extensively made use of for the fabrication of overcoats and other waterproof garments. In the manufacture of these goods the first step is to prepare a dough or paste suitable for spreading on the material. If the vulcanization of the coating is

Double-texture fabrics can be produced by employing similar apparatus, but double; and the two textures, which are vulcanized simultaneously, are brought into contact immediately after the solution has acted on them. Under these circumstances they adhere, but when made up into coats, etc., these double textures can be separated at the edges by the application of benzole, this being a matter of great convenience in joining the various parts of a garment together.

Spread goods are often varnished by the application of a dilute ammoniacal solution of shellac, the surface of the goods being generally prepared for the reception of this by the application of water, or of water containing a trace of an alkali, soap, or ox-gall, either of which facilitates the

A large number of specimens of spread goods are on the table, these having been supplied by Messrs. William Currie & Co., of Edinburgh, the Silvertown Company, Messrs. Cow & Co., Messrs. Anderson, Abbott, and Anderson, and

others.

Spread sheets, already referred to several times, are made by spreading a mixture of sulphur or other vulcanizing material and softened rubber on cloth previously charged with a mixture of paste, treacle, and glue. The required thickness having been built up, vulcanization is effected by means of steam, and the prepared cloth, being softened by the action of water, can be easily removed from the sheet of rubber. Sometimes the required thickness of spread sheets is built up on two separate pieces of the prepared cloth, and the adhesive surfaces of the rubber being placed in contact, they unite, after which vulcanization is effected in the usual way, and the cloths are removed.

Spread sheets, prepared by this latter method, show the marking of the cloth on both sides, while those prepared by the first method are smooth on one side. As a general rule spread sheets are more perfectly elastic than calendered sheets, as the rubber undergoes less mechanical tearing or deterioration. They are generally

preferred for cutting into threads.
Mr. Sexton, the representative of the National
India-rubber Company, of France, has kindly
lent me a well-assorted set of specimens illustrat-
ing the use of caoutchouc in the manufacture of
boots and overshoes; this firm turning out over
two millions of pairs yearly. Articles of this kind
are generally made out of a mixed rubber, which
is callendered on to woven or knitted fabrics,
these having been previously frictioned. After the
articles have been made up and varnished they are
cured in stoves or ovens, heated from 130° to 150°
Centigrade.

Several processes have been proposed for the desulphurization of old vulcanized caoutchouc, but the success attending endeavors of this kind has been very limited. The incorporation of old rubber with new has been referred to already. The use of old rubber in making the admirable floor-cloth known as kamptulicon is a very useful application of it.

the resisting obstacle, or into that molecular vi- with the writer in the method of its application bration which is recognized as heat. Direct the first use of water to control the temperature friction refers to the case where the two bodies of the bearing surfaces of oil-testing machines is are in actual contact, and mediate friction where due to Monsieur G. Adolphus Hirn, and described a film of lubricant is interposed between the sur- by him in a paper on the subject of friction, read faces; and it is this which applies to nearly every before the Société Industrielle de Mulhouse, June motion in mechanics where bodies slide upon 28, 1854. M. Hirn, however, confined his ateach other. The coefficient of friction is the re- tention chiefly to the determination of the melation which the pressure upon moving surfaces chanical equivalent of heat, as measured by the bears to resistance. I have devoted some time amount of heat imparted to the circulating to the examination of this subject, in the inter- water, expressed in the work of friction. His inests of the Mill Mutual Insurance Companies of vestigations of lubrication with this apparatus New England. In this report of my work upon were confined to the friction of lard and olive the measurement of friction of lubricating oils, I oils, at the light pressure of about one and fourCURVES SHOWING CHANGES OF COEFFICIENT OF FRIC- tenths pounds to the square inch. Mr. TION UNDER VARYING CONDITIONS.

.10

.20

COEFFICIENT OF FRICTION.

Chas. N. Waite, of Manchester, N. H., has independently, and I believe originally, made use of water in a friction machine, and has performed good work in the limit of his experiments.

A protection of wool batting and flannel, to guard the discs against loss of heat by radiation, diminishes the escape of heat to about two degrees per hour, which loss is not appreciable when observations are taken within a few seconds'interval. A thin copper tube, closed at the lower end, reaching through the cover, extends to the bottom of the disc; the bulb of a thermometer is inserted in this tube and measures the temperature of the discs; an oil tube runs to the center of the disc, and a glass tube at the upper end indicates the supply and its rate of consumption, and also serves to maintain a uniform head of oil fed to the bearing surfaces. The rubbing surfaces of both discs were made to coincide with the standard surface plates, in the physical laboratory of the Institute of Technology, and their contact with each other is considered perfect.

After this surface was finished, the bronze disc was treated with bi-chloride shall restrict myself to a description of the appa- of platinum which deposited a thin film of ratus designed especially for the purpose, the platinum upon the surface. Upon the applimethod of its use; and the results obtained with cation of the discs to each other the steel a number of oils in our market which are used disc rubbed off the platinum from all parts of for lubricating spindles. Previous investigation the surface, showing the perfection of contact. of nine different oil-testing machines used showed This nicety of construction enables a film of that none of them could yield consistent dupli- oil of uniform thickness to exist between the cate results in furnishing the coefficient of fric-surfaces, and the resistances are not vitiated tion. The operation of these machines, by their by the collision of projecting portions of the disc failure to obtain current data, adduced certain with each other. The rounded end of the upper negative evidence which established positive con- shaft fits into a corresponding depression in the ditions as indispensable in the construction of a top of the upper disc. This method of connection machine capable of measuring the friction of oils. retains the disc over the proper center, yet it is The following circumstances must be known or allowed to sway enough to correct any irregularpreserved constant,-temperature, velocity, pres- ity of motion caused by imperfection of construcsure, area of the frictional surfaces, thickness of tion or wear of the lower disc. To obtain the the film of oil between the surfaces, and the me- desired condition of pressure, weights are placed chanical effect of the friction. In addition to the directly upon the upper spindle. The axes of the foregoing conditions, the radiation of the heat upper and lower spindles do not lie in the same generated by friction must be reduced to a mini- straight line, but are parallel, being about onemum, and the arrangement of the frictional sur- eighth of an inch out of line with each other; faces must be of such nature that no oil can such construction, giving a discoid motion, preescape until subjected to attrition. To measure vents the disc from wearing in rings and assists the frictional resistance at the instant of a given in the uniform distribution of the oil. An arm is temperature, and at a time when both tempera-keyed through the lower part of the upper asurements of the Friction of Lubricating Oils. ture and friction are varying, requires a dynam-spindle and engages with projections upon the ometer which is instantaneous and automatic in upper disc. Upon this arm, which is turned to its action.

Kamptulicon consists of old rubber and cork, both materials being brought into a state of fine division, after which they are incorporated by heated rollers, and then rolled out into sheets. You need not seek far for a specimen of this material, as the floor of this room is covered with it. The Britannia Rubber and Kamptulicon Company have lent me the figured and patterned specimens which are attached to the wall, and also other articles, which illustrate the various uses of this material. Knife-cleaning boards are often covered with it; and when made up into sheets, two inches thick, it is extensively employed as a means of deadening the effects of concussion. These thick sheets are particularly adapted for covering the floors of riding schools, or for lining cells in which violent lunatics are confined.

[To be continued.]

BY C. J. H. WOODBURY, BOSTON, MASS.

A paper read before the American Society of Mechan-
ical Engineers.
The resistance existing between bodies of
fixed matter, moving with different velocities or
directions, presents itself in the form of a passive
force which results in the diminution or the de-
struction of apparent motion. Modern science
has demonstrated that this destruction is only
apparent, being merely the conversion of the

force of the moving body into the oscillation of

the arc of a circle, whose development is two and The apparatus consists of an iron frame sup- one-half feet, a thin brass wire is wrapped upon porting an upright shaft surmounted by an an- this arc and reaches to the dynamometer, so that nular disc made of hardened tool steel. Upon the tension of the dynamometer is tangential and the steel disc rests one of hard bronze the leverage is constant for all positions of the (composed of the following alloy-copper 32 upper disc within its range of motion. The dynaparts, lead 2 parts, tin 2 parts, zinc 1 part) in the mometer consists of a simple bar of spring steel form of a cylindrical box. Water is fed in at one fastened at one end, and bent by the pull applied side and a diaphragm extending nearly across the at the other. Its deflection is indicated by a interior produces a uniform circulation before dis-pointer upon a circular dial, the motion of the

charco Although this vaa

The apparatus is used in the following manner erature of 14,500 pounds of water one degree to measure the coefficient of friction of oil. After Fahr., from 39° to 40°. One pound of hydrogen cleaning with gasoline and wiping carefully with when similarly burned will raise the temperature wash leather, the discs are oiled and run for of 62,000 pounds of water in the same amount; about five hours, being kept cool by a stream thus it will be seen that the heating power of hyof water circulating through the upper disc. drogen is more than four times as much as carbon. From time to time they are taken apart, cleaned The next element in the table is oxygen; this and oiled again. After using any oil, even if the is a supporter of combustion, and in order to get discs are afterwards cleaned, the results with the into the fire we arrange openings in the grate oil subsequently used give the characteristics of bars for air to pass through, and thus allow the the previous oil, and it is only after 35 to 45 miles oxygen in the air to combine with the carbon or of attrition that these results become consistent hydrogen in the fuel, and in this way heat is genwith each other; each succeeding result, mean-erated, as we usually express it. The presence time, approaching the final series. This seems of oxygen in any fuel to be burned is a bad thing, to indicate that friction exists at the surface of the because it lowers the heat producing power of two dises between the film of oil acting as a the fuel; and it does it in this way: When oxygen and hydrogen are present in the same fuel they unite to form water. Oxygen unites with oneeighth of its own weight of hydrogen to form water; thus one-eighth of 41.3 equals 5.16 per cent. of hydrogen rendered useless in the fuel because of the presence of oxygen in it at the same time.

washer and the globules of oil partially embedded within the pores of the metal. If the dense bronze and steel retain the oil despite attempts to remove it, how much longer must it require to replace the oil in machinery with a new variety whose merits are to be tested. These experiments confirm the wisdom of the increasing use of cast iron for journals, as its porosity enables it to contain and distribute the lubricant.

When the discs are ready to test the oil the apparatus is cooled by the circulation of water; the flow of which is stopped when the machine is started. At every degree of temperature, the corresponding resistance is read on the dynamometer. When the thermometer indicates a temperature of sixty degrees, the counter is thrown in gear, and the time noted. When one hundred and thirty degrees is reached, the counter is thrown out of gear, and the time noted. This not only gives the velocity of the rubbing surfaces, but the number of revolutions required to raise the temperature a stated number of degrees, and is a close criterion of the oil. The coefficient of friction is the ratio of the pressure to the resistance.

Total heat units in one pound of wood....
This does not take into account the loss of heat
occasioned by the presence of 1.05 per cent. of
nitrogen, which is not a supporter of combustion,
but which is heated to the same temperature as
the other gases in the fire.

It should be understood that the above total
number of heat units in one pound of wood is for
wood perfectly dry and specially prepared for
analysis. Ordinary wood, not dry, will contain

6,500

Difference in favor of coal.. To put it in another shape, one pound of coal is equal to 2.36 pounds of wood.

When good bituminous coal is used under a boiler with chimney draft, the combustion being to the furnace, it ought to evaporate ten pounds complete and no great excess of air admitted of water per pound of coal, good wood will evaporate about five pounds. There is not much difference in the heating power of the several kinds of wood when equally dry and taken pound one ton in weight equals. for pound. If we take 2,240 pounds per ton, then: .1.2 cords white pine spruce "Southern pine

.97

heating power of good dry wood at 0.4 that of It is customary in evaporative tests to fix the

good coal.

The following table shows the resistance of about one-third of its weight of water. To evap worth $4.75 per ton, the relative price for hard

friction at 100° 500 revolutions, for various pres-orate this requires an expenditure of a portion of

losses incident to burning wood we have scarcely
more than 5,500 heat units, as actually available

For further detailed results, reference is made in the combustion of one pound of wood.
diagram B.

maple would be $.75x51-$2.42 per cord, or $4.75 X.60 $2.85 per cord for southern pine, and in this manner for any other wood given in the table.

Whatever kind of fuel may be selected for reg

ular use, its nature will have to be studied and the fire regulated accordingly. Some kinds of coal will not stand urging as much as others, on account of its forming a clinker which is not only difficult to remove from the grates, but acts as a hindrance to a free and perfect admission of air

to the burning fuel. Coal of this kind should be spread over as large a grate area as possible, that the combustion be slow. Coals which burn to a red ash are more likely to yield a clinker in an intense fire than coals burning to a light brown or white ash.

ASBESTOS.

One of the most interesting minerals in the mineral kingdom is that known by the name of asbestos or asbestus. Its name; derived from the Greek, signifies "unconsumable." It belongs to the amphibole or hornblende class in the mineral kingdom, and bears a close resemblance to some other members of that class, such as achnolite and tremolite. It is found more or less abundantly in all countries, and exists principally in the serpentine, mica strata, and principal crystaline rocks. Its chemical composition is chiefly silicia, magnesia, alumina, and ferrous oxide, and it consists of fine crystaline threads or fibres, glistening with a silky lustre, and varying in color from white to gray, yellow, blue, or green. The mineral exists

in several varieties; each of which possesses some distinct characteristic. Its variation ana na

such as clothing for firemen and others, bricks for dwellings, paper for deeds, and numerous others of a like nature. In order to show why these various ideas, inventions and patents are not in great requisition at the present time, it will simply into yarn, may be further woven into ropes from his ingenuity and enterprise, granted him a

pension, which has been the support of himself First of all, as asbestos was known to resist the able for glands, valve-stems, cocks, &c., and has merest accident that Colonel Drake's attention and family for several years. It was by the action of fire, it was thought that it would prove been found to work successfully under the highest 1858. Half a century before that date old Nat was first directed to the value of petroleum in an important article in the manufacture of clothpressure of steam. This packing being indes- |

ing, more especially for firemen and such. To tructible, either by heat or oil, need not be chang. Carey had peddled the peculiar oil which was weave the fibres was not a very difficult matter, ed when once "packed" for a long period, as it skimmed in small quantities from the waters of lasts for some months without renewal. The ecowith flax, working the mass into cloth, then sub-nomical advantages resulting therefrom are too gative and liniment. He called it Seneca oil,

obvious to need remark. The large-sized ropes had imparted to the whites the secret of its poware used for packing cylinders, pumps, &c., and have been applied to the former purpose on some ers. Its fame as a medicinal agent was purely of the principal steamers. These packings are local, when Carey, with vials of the stuff, plodded water, and is rubbed with the fingers. It is then either woven from the yarn, or are made up of from hamlet to hamlet and established a demand soaked in oil, mixed with a little cotton-waste, the unwoven or "loose" fibre, covered tightly for it that brought him no small profit. An atand spun in the ordinary way. The application with a coating of cotton. This covering of course tempt by General Franklin to introduce this soon wears off, leaving the asbestos to resist the "great natural medicine" to a Southern market