the triangular gutter found by the first excavation, and as the valve sinks to give a greater supply, this gutter gradually increases its sectional area until it is assisted by the second, and finally the third exca

vation.

In this manner a small amount of gas is passed through a channel of small dimensions and great length; but when a large amount is required, the valve presents the area of the three excavations, and at their largest section.

With ordinary pressures the valve has one inch of motion for use with one burner, whilst the two remaining inches will furnish a supply for twenty burners.

The gas holder H is a frustrum of a cone, the result of which form is to present to the lifting pressure of the gas a constantly diminishing area as it sinks into the fluid to open the valve, and consequently gives

w

an increasing pressure whilst increasing the supply of gas. The amount of coning has been adjusted by experiment so as to increase the outlet pressure sufficiently to compensate for the loss of pressure in the fittings by the addition of many lights.

The fluid preferred for use in the tank is crude glyceringe, as it does not freeze easily nor evaporate, and has no corrosive influence upon the metal of the in

strument.

The experimental trials made with the instruments were as follows:

For delicacy of adjustment. Gas was passed through the regulator to a branch upon which were burning twenty-one lights. All of these with the exception

of one (a union jet at its maximum) were suddenly extinguished by a master cock, the single burner remaining without change, the pressure gauge showing a vibration of less than one-twentieth of an inch.

The pressure upon the inlet of the regulator was then increased successively to two and three inches without change upon the gauge upon the outlet of the regulator, as was also the case when one burner or all were lighted.

To show the result of checking off at the meter stopcock, as is frequently done where no regulator is used, the branch with the burners was connected directly to the street main without the intervention of the regulator, ten of the burners lighted, and the pressure adjusted by a stopcock to eight-tenths of an inch. When all but one were extinguished, the pressure rose to thirteen-tenths, the burner blowing. When twenty burners were lighted, the pressure fell to three-tenths of an inch.

An experimental trial was then made as to the quantity of gas consumed by the burners when under regulation to their maximum econ

omy, and also the amount consumed by the same burners when subjected to the ordinary variations of street pressure, as observed during the present evening.

The result showed that with the regulator there was uniformly 78 cubic feet of gas per hour consumed by twenty-one burners, or 3.7 cubic feet per hour per burner. Whilst without the regulator the same burners consumed from 106 to 140 cubic feet per hour, the average being 126 cubic feet, or 6 feet per hour to each burner, the amount of light being not nearly proportionate to the increased cost. The burners. being in the first instance properly adjusted to the wants of the consumer, all increase of light would be waste and loss.

Again we would call your attention to a plan for sharpening the teeth of saws, by grinding on a wheel of emery and vulcanite or hard rubber, the invention of Joseph F. Tuder, of this city. The effect of grinding on a wheel is, of course, to give a hollow face to the teeth, which causes them to cut better and for a longer time than when they are made flat or even rounded, as must be the case in filing.

The famous instrument maker of Paris, Deleuil, has brought before the French Academy an air pump in which all lubrication and packing are dispensed with. The piston is made very long, (twice its diameter,) is fitted very accurately to the cylinder, and has a number of horizontal grooves cut around its surface.

It is then found to be air-tight by reason of the capillary attraction of the air in the narrow space included between the cylinder and piston. With a small receiver on the pump plate, a vacuum of four millimetres of mercury can be obtained by this apparatus.

In the Practical Mechanics' Journal for September, we find the translation of an article on the mechanical puddler employed at the Closmortier forge, by MM. Dumeny and Lemut. This article is accompanied by many drawings, and is of great interest as showing the exact means employed in this important modification of iron working, and many of the results obtained by the new method.

A report has been made by the Société Industrielle de Mulhouse, on the Lenoir gas engine, the main conclusions of which may be thus briefly stated:

1st. That this motor consumes per horse power per hour 105 cubic feet, while a steam engine of like effect would consume 11 lbs. of coal in the same time.

2d. The gas engine requires an immense amount of oil, as much, in fact, as 2 pints per horse power per day.

3d. The gas engine, again, requires constant and close attention on the part of the person running it, rendering it impossible for him to do any other work at the same time.

4th. The cost and care of the battery working the induction coil, which ignites the gas, is an item not included in steam motors.

All these are drawbacks to the machine in question. On the other hand, it presents the following advantages:

1st. It consumes fuel only while actually running. Thus, when

required for intermittent work, it may compare well even in economy with a steam engine, whose fire must be constantly burning. 2d. Its perfect freedom from danger.

3d. Its convenience of form, admitting of its introduction into any building, as it requires no furnace, fire, or the like.

Lastly, under this head of mechanics, we would bring to your notice this little apparatus called an atomizer, for scattering perfumed or medicated liquids in impalpable spray through the air of an apartment. It consists (as you see) of two glass tubes placed at right angles to each other, and kept in position by a little bracket of brass. We dip the longer of these in a vessel containing the liquid to be scattered, and then blowing through the other across the upper end of the first, produce a rarefaction in this, which causes the liquid to rise in it so as to be scattered in a fine mist from the upper end by the powerful blast of air. This instrument is invented by S. Maw, of London.

Optics. Under this head we would introduce to your notice a plan for constructing cheaply large parabolic mirrors, of an enduring and light material, invented by Mr. J. Marshall.

In this case the frame or mould is formed of thick paper, moulded or otherwise worked into the required shape. To the inside of this are attached scales of mica, plated with metallic silver. The result is a reflector, light, durable, easily repaired, powerful in its reflecting action, and cheap in its first cost. Several of these mirrors, of various dimensions, were then exhibited, and their efficiency practically demonstrated. One of them, intended for lighting a skating pond, was four and a half feet in diameter.

Attention was here directed to a plan by which chemical and other reactions could be exhibited to a large audience, by the employment of a magic lantern, but the experimental demonstration of these was deferred until after the adjournment of the meeting.

Chemistry. We have to notice two important plans for the preparation of the common alkalies directly from mineral substances found in great quantities and easily obtained.

Potash from feldspar. Feldspar, fluorspar, and chalk are pulverized, mixed, and calcined. Fluoride of silicon is disengaged, silicate of lime is formed, and the potash set free,-may be dissolved out by boiling water, and freed from any lime present by carbonic acid. Some feldspars are, however, found to contain large quantities of soda, and yield on treatment that base.

Soda from cryolite. Cryolite and lime are pulverized and calcined, insoluble fluoride of calcium is formed, and a soluble compound of alumina and soda. This is dissolved out with water, which is then treated with carbonic acid, by which carbonate of soda is formed, and the alumina is precipitated. The Pennsylvania Salt and Alkali Manufacturing Company sent out last winter their chemical superintendent, Mr. Henry Pemberton, together with Mr. S. Lewis, to Copenhagen, where these gentlemen arrived about the 1st of December. They there made arrangements with the owners of the cryolite mines in Greenland,

Messrs. Shure & Sons, and with the Danish government, for the right of mining that material. Ships were then chartered in England, in Quebec, and in our own ports, to proceed to Ivigtus, Greenland, lat. 59°, load with the mineral, and bring it to this port. Six thousand tons have thus been imported up to this time, and a portion of the material is already undergoing treatment at the works of the company near Pittsburgh.

At the request of the members present, Mr. William Sellers then stated some of his observations during a late visit to England, as follows:

Whilst in England, I noticed great progress in all the industrial interests, the most remarkable being in the manufacture of steel. Formerly this business was confined to the manufacture of steel for cutlery purposes and other small objects, the use of it in large masses being unknown; but within the last six years, the general introduction of the Bessemer process, as well as that employed at Mr. Krupp's works in Germany, have revolutionized the trade, so that work which, under the old system, would require an immense number of hands, can now all be done upon the Bessemer plan by a few, making the steel thus produced comparatively cheap, so that it can be applied to ordinary purposes where iron has heretofore been used. It is probably true that this process will not produce the best quality of steel, but the material obtained is, at least, far better than any other equally cheap. By the Bessemer process, up to the point of converting into steel, labor is almost dispensed with, the operation of puddling being entirely abolished. The various movements required are all performed by hydraulic machinery controlled by one man, and it is interesting to see with what facility large masses of molten metal are handled, ten tons often being taken off at a heat. The pig metal is melted in an ordinary reverberatory furnace, and the speigleisen in another smaller one from which they are run into the converting vessel. This is a large egg-shaped vessel open at the top, and suspended upon trunions, so that it may be tipped upon an angle in order to bring its upper or open end under the spout, from which it receives its molten charge of iron. The bottom of this vessel is double, so as to form an air chamber, communicating through the trunions with the blowing cylinders, which produce the blast. The tuyeres are between the air chamber and the inside of the converting vessel, and when this is tipped on one side to receive its charge, the tuyeres will be above the molten iron. The blast is then applied, the converter tipped back to a perpendicular position, and the air rushes through the molten mass, burning out its carbon. When this is accomplished, the converter is turned on its side, the blast shut off, and the mouth passed under another spout to receive its charge of speigleisen. This produces a violent ebullition, and when this has subsided the conversion into steel has been completed.

The converter is now once more tipped upon one side, and the steel is poured into the ingot moulds, which are arranged in a semicircle about the centre of the hydraulic crane which carries the

converting vessel, the whole process being completed in almost as little time as it requires to describe it. After the ingots are sufficiently cool, they are removed to the heating furnaces, and from this point to the hammer or rolls, the subsequent processes are the same as in the manufacture of iron, although requiring machinery of more massive character, owing to the greater density of the material to be operated upon. In the process followed at Krupp's, and other similar works, the metal is melted in small pots, and then poured into one large enough to contain the quantity required for the intended casting, and from this it is let into the mould by withdrawing a plug in the bottom. I have seen gear wheels of excellent finish cast in this way, and large quantities of railway wheels and tires are thus made, the field for its use continually widening. The character of the steel made upon this process is as yet much superior to that made upon the Bessemer principle, and, it will be observed, there is one radical difference, the one rigidly excluding the air from the molten metal, whilst in the other, it is intimately mixed, but whether this is the cause of the difference in quality must be determined by more extended experience. Those engaged in the manufacture expected to make farther improvements, and from what I learned of their operations I believe that in a few years they will cast as large a piece as a twenty-inch gun of steel.

PROF. ROGERS.-They are making Bessemer steel in Troy, N. Y. Mr. Lamborn, of the Iron and Steel Association, is not here, or he would tell us something about it. Did you observe anything new in machine tools.

WM. SELLERS.-I knew they were preparing to make Bessemer steel there, but was not aware that any was produced as yet. The introduction of steel in masses has necessitated larger and stronger machine tools, but I did not observe any other change; that of size, however, is remarkable. Sir Wm. Armstrong's works, at New Castle, in the Ordnance Department, contain many fine specimens of tools, but they are for special purposes. The tools required for rolling and dressing cast steel tires are also remarkable for their enormous size and strength.

COLEMAN SELLERS.-Is the tire round, or is it necessary to turn it? WM. SELLERS.-They turn it out on the inside at the works. They have made special machinery for the whole of this work, and nearly all steel tires as yet have been made from pot metal. The process of casting from pots is very interesting. From the great number of pots used, and the necessity of bringing them to the proper heat, and pouring into one reservoir at the same time, it is necessary to have all the men as thoroughly drilled as a regiment.

COLEMAN SELLERS.-You spoke of the movement of these large masses of metal. How is it accomplished?

WILLIAM SELLERS.-Entirely by hydraulic pressure. All the operations are performed in that way, excepting in the rolling of armor plates; in that case they use a traveling crane over head, and upon that