had not yet reached its maximum, Another bar of the same kind, after a long service, had a permanent elongation of 3 per cent.

If it be remembered, that bars while exposed to the fire undergo another temporary elongation; we must agree with M. Brix, that an allowance should be made in a bar which has not as yet been used, amounting to 4 per cent. of its length, for this cause of elongation. The bars must, of course, be sufficiently long to stand between their supports when cool, but it seems that hitherto sufficient room has not been given for this permanent expansion in laying down new bars.

On the Fatigue and consequent Fracture of Metals.—At a meeting of the Institute of Civil Engineers of London, Mr. F. Braithwaite communicated a paper, in which he points out the different consequences that will result to masses of metal, according as they are obliged to bear a continuous strain, or one repeated at intervals. In the latter case a certain disturbance of the particles takes place, the metal becomes sooner deteriorated, and ultimately breaks from the action of the reiterated strain. He contends that, presuming adequate dimensions to have been given to girders, and the stipulated weight not to have been exceeded, there is not much chance of accident; but any repeated deflection must be productive of danger, which can be averted only by altering or replacing the parts deficient in strength, and maintaining a rigid supervision, whether of beams loaded, of machinery, or of the rolling stock on railways.-Artizan for July.

MACHINERY, MANUFACTURING TOOLS, AND INSTRUMENTS IN GENERAL.

On Bourdon's spring Manometers.-Although the oscillations of a mercurial column furnish perhaps the best means for measuring moderate changes of pressure in elastic fluids, it has been long a desideratum to obtain something better suited to the measurement of very high pressures. This seems to be the most important advantage claimed for the inventions of M. Bourdon, of which we propose to treat in this present notice.

The principle upon which these manometers is founded is the variation of curvature which must take place in a tube of elastic metal, shaped like an incomplete ring, with a flattened cross section, from changes in the relation between the internal and external pressure on its sides.

It is found by experiment that when such a tube is placed in a medium which exercises a constant pressure, if it be filled with fluid, so as to increase the pressure within it, the curvature lessens as it distends, and the ends of the incomplete ring diverge. When the pressure of the internal fluid is less than that of the surrounding medium the curvature increases, and the ends of the incomplete ring are found to approach. Conversely, if the internal pressure were constant, an increased pressure of the external medium will cause an increase of curvature, and a diminished pressure a diminution of the curvature of the imperfect ring, If a perfect vacuum were formed in such a tube hermetically sealed, the internal pressure would be zero and constant, while the external pressure would depend on the conditions of the surrounding medium. Such a tube placed in the air would thus constitute a barometer.

It is easy to explain how the distension and contraction of the sides of the tube can produce the changes of curvature in tubes of a circular form.

Let a represent the angle subtended by an arc of a circle, whose length is L, with the radius R; then as the angle at the centre of a circle is directly as the length of the arc which it subtends, and inversely as the radius

a =

L
R

=

? being the length corresponding to the radius r. If we suppose a section made in the plane of the ring, R may represent the radius of the outer circle bounding that section, and r the radius of the inner and smaller circle. Let d represent the interval between the two circles. Then,

Let d' represent what d becomes by a dilation or contraction of the sides of the

tube, the lengths of the arcs remaining constant, a changes to a', and therefore, Finally, we have

ď

=

L-I
a'

d a'
d' a

=

Consequently the angle at the centre

will be inversely as the distances of the flattened sides of the tube, and therefore the curvature of the ring will also be inversely as these distances. If the inner and outer parallel edges of the section of the ring are not circles, we may suppose them made up of a series of circular arcs, each arc having for its radius the radius of curvature at that point. The above result will manifestly hold good for every corresponding pair of these arcs in the two curves, and consequently the approach or separation of the two curves will be followed by an increase or diminution of the curvature of the ring.

In order that such a tube could be applicable to the measurement of pressures it should follow that its changes of curvature would be proportional to the changes of external or internal pressure. In other words, the resistance of the tube to changes of flexure should not be variable. Let the opposite flattened sides of the tube be decomposed into a series of bands or filaments, each of these will undergo similar changes of flexure with the same pressures as straight bands of the same dimensions. But the flexure of such a band is measured by the versed sine of the are which it forms under pressure, and is proportional to the intensity of that pressure-a result completely verified in the case of ordinary springs consisting of solid slips of metal, and which appears very approximately true in the case of hollow slips of metal such as the tubes in question. In point of fact, these might with great propriety be called hollow springs, and the instruments of which they form the base, spring manometers.

It is easy to conceive how the movements of these hollow springs can be measured by a suitable graduation. It only requires to have this graduation made by a comparison with mercurial column manometers, in order that the instruments would be independent of variations in the proportionality of the flexures of the tubes to the pressures, and such a course seems to have been hitherto very successfully adopted. The graduation has usually been on a circular are of more or less dimensions, the movements of the ends of the hollow spring being transmitted by lever-work to a traversing needle.

An objection to these instruments seems to arise from the possible changes in the elasticity of the substance composing the tubes, whereby the indications of the needle would ultimately be rendered utterly valueless. But it is stated that hitherto, even at the extreme limits of their indications, no perceptible alteration has taken place in the accuracy of the instruments, and it seems extremely probable that one of them would continue to give correct results as long as the elasticity of the hollow springs is not too severely tried.

The invention was first suggested to M. Bourdon by an accidental observation. In January, 1849, he was constructing some machinery, to which he had to connect a worm-shaped tube. This tube having been bulged through some mismanagement, he was obliged, before using it, to stop it at one end, and to force water in at the other by means of a hydraulic press, until the pressure, overcoming the resistance of the metal, would smoothen out the creases and bulgings, so as to bring it back to its proper shape.

During the injection of the water, a very decided bending of the entire tube was observed, according as the parts which had been bulged commenced to swell out from the pressure. M. Bourdon immediately saw the value of this phenomenon with reference to the measurement of the pressure of elastic fluids, such as steam and the gases, and after a series of trials, was at length enabled to present his manometer at the Paris Exhibition of 1849, where he received the Gold Medal. At the Exhibition of All Nations in London, he obtained a Council Medal; and in the Reports of Juries, p. 301, is a short but favourable notice of his inventions. The inventor proposes to apply these hollow springs to different kinds of manometers, applicable to different purposes. Among these are what he calls maxima and minima manometers, which, in the case of steam engines, and especially locomotives, will be doubtless found more suitable than instruments depending on the mercurial column. He also proposes to construct manometers for the hydraulic press, and is said to be actually constructing one for a carbonic acid solidifying apparatus, that will indicate the pressure of 300 atmospheres.

It is easy to conceive, after what has been stated, how barometers can be constructed on these principles. Those which have been actually made very closely resemble the Aneroid barometer in outward appearance, though the internal arrangements are in many respects essentially different.

The American Tunnel'ing Machine.-Talbot's "tunnelling machine" has been tried with complete snecess; and it has been demonstrated that mountains of primitive stone and the hardest rocks in the earth can be successfully and economically tunnelled by the agency of steam applied to this new invention. The slow and expensive process of perforating by the drill and blast will be thrown aside. In the trial experiments, the machine moved by a steam engine, cut an excavation of 17 feet in diameter through the hardest rock, at the rate of about 3 feet in two hours. The process consists in cutting and crushing the rock by means of rotating discs of steel, in successive series, which describe in their movements segments of circles from the centre to the circumference of the tunnel, with a gradual motion around the common centre; while the steam-engine is constantly pressing the machinery on a direct line with the axis of the tunnel. The newest and most extraordinary feature of the application of this power, consists in the combination of different sets of discs, which act upon the entire surface, to be excavated by a system of gradation perfectly regular, and by a power that is irresistible. The machine, which worked most satisfactorily, is made entirely of iron, and weighs about 75 tons, exclusive of the engine and boiler. One of the most interesting features of the experiment was when the machine began to cut the rock in an oblique direction, for it was observed that those discs or arms which were cutting the stone, moved with the same facility that those did which were playing in the air. Gradually the cutters described their curve, the great face-plate of 17 feet constantly revolved, throwing out and drawing back its arms with complete regularity, seizing and crushing the rock with irresistible power. Only four men are required to work this machine to the greatest advantage; and two of them confine their attention to the engine which propels it. There is no necessity for suspending the work day or night, except for those intervals when the cutters have to be sharpened, or new ones substituted. The amount of time and expense which is saved by the operation is almost incredible. This machine evidently supplies a want which has been felt in every department of civil-engineering. It will revolutionize the whole system of railway construction, and is regarded as one of the most wonderful inventions of any age.-Jameson's Edinburgh Philosophical Journal for July.

Flax Breaker.-John Ilinde, of Schenectady, New York, has taken out a patent for a new form of flax breaker. It consists in passing the flax straw between a ribbed or fluted endless apron, and a series of fluted rollers, which have a rolling motion over its surface. The action of this sheet or apron and the rollers, is intended to resemble the action of the human fingers in divesting the material of its woody substance.-Scientific American, No. 41, June 24th.

Sawing Machines.-John I. Squire, of St. Louis, United States, has invented some new improvements for re-sawing stuff which has previously been sawn out of the log, and making it into pickets, &c. A radius guide is applied to the saw for guiding it as it enters the stuff, insuring its true movement, and preventing its vibration. The saw is hung in a sliding frame, in such a manner that it (the saw) can be adjusted as it is worn by use; and it also permits of saws of different sizes being used. Feed rollers are placed within the sliding frame for gauging the stuff to be sawed, presenting it to the saw, and guiding it while being sawed.— Scientific American, No. 40.

Planing Wood Mouldings.-An improvement has been made in planing mouldings, which consists in the combination of feed rollers and stationary cutters, by which the mouldings are planed much faster than by hand-the method of finishing them at present. The rotary moulding machines now in general use do not finish the mouldings smoothly; indeed, the sides are not smoothed at all, consequently neat joints cannot be made of such stuff-but require the hand plane. This machine is designed to finish the work accurately.—— Scientific American, No. 40, June 17th,

Mortising Machine.-Hiram and S. H. Plum, of Honesdale, Pensylvania, have invented an improvement in mortising machines, which consists in the employment of two chisels, for cutting the ends of the mortise, and a reciprocating planer working horizontally, for cutting out the wood between the two end chisels, as the latter are forced gradually into the wood.-Scientific American, No. 40.

Improved Tenon Machine.—The great difficulty in the tenon machines hitherto constructed, has been the expense of time and labour, occasioned by shifting the timber from its positions, and often the employment of two machines on the same piece of work. ̊C. P. S. Wardwell, of Lake Village, New Hampshire, has proposed to obviate this with an improvement, which shall combine all requisites in a single machine. His plan consists in a peculiar arrangement of vertical saws, for squaring the end of the rail, and for forming the shoulder, and horizontal saws combined, for cutting the tenons themselves, whereby a reversal of the rail is rendered unnecessary. By the addition of one or more cutters between the horizontal tenon saws, working in combination with the shoulder saws, the capacities of the machine are greatly increased. A suitable number of nuts and set screws, to keep these saws in the places to which they are shifted, to secure the desired angles of cut, completes the arrangement.-Scientific American, No. 43, July Sth.

Machine for cutting Shoe Welts.-S. I. and C. II. Trofatter, of Salem, Massachusetts, have invented an improved arrangement of machinery for cutting leather to be used for the welts of boots and shoes. The object effected is the cutting of two welts from the same thickness of leather at one operation, both being alike in every respect. When welts are cut by hand, only one is obtained, generally speaking, from one thickness of leather. This machine cuts out the welts with great rapidity, is neat and not expensive.—Scientific Americun, No. 40. Improved Auger.-Isaac W. Hoagland, of Jersey City, New Jersey, has patented an improvement in augers, the nature of which consists in having the cutting portion of the auger male detached from the screw portion, and attaching the cutting part to the screw part by means of dovetails and screws. appears to be an excellent improvement, for the screw part by this plan can be made to answer twenty cutting parts as they successively wear out.—Scientific American, No. 40.

IMPROVEMENTS IN THE MANUFACTURE OF TEXTILE FABRICS.

This

Improvement in Looms.-William Henley, of New Salem, North Carolina, has taken out a patent for important improvements in looms, applicable alike to hand and power looms, but made chiefly with a view to their application to hand looms. One improvement consists in a certain means of throwing the shuttle; and the other improvement relates to operating the harness, both of which derive motion from the lay, so that the swinging of the latter sets the whole of the loom in motion-in other words, by swinging the lay, all the working parts of the loom are moved. In common looms, the shuttle, the lay, and the harness, are operated by their distinct and separate movements. These improvements appear to be of great importance to the linen and muslin trade of Ireland and Scotland.

IMPROVEMENTS AND INVENTIONS CONNECTED WITH CHEMICAL PROCESSES.

Improvement in the manufacture of Bakers' Yeast, by M. C. Gutkind of Paris. -The new method consists in completely saccharifying the starch contained in barley. The barley is slightly malted, dried in a rapid current of warm air, taking care to prevent smoke coming in contact with the grain. The malt thus prepared is reduced to the condition of the finest flour possible, without bolting it; that is, the flour and bran should not be separated This flour is introduced into a vat the size of which varies according to the quantity of yeast intended to be prepared at each operation. Water at a temperature of 400 centigrade (104° Fahr.) is introduced into the vat suflicient to make the flour into dough like that for making bread; this dough is then diluted with a further quantity of water, at the same temperature, to the consistence of porridge. M. Gutkind prefers using, for every 100 kilogrammes of flour (= 220-48 lbs.), 2 hectolitres (= 44 gallons)

of warm water. When the porridge is made, it is introduced into a boiler, where it is gradually heated to 810 centigrade (= 177·8 Fahr.) As soon as it reaches this temperature, the fire or steam, whichever be employed, is arrested, in order that the temperature of the porridge, become sensibly more fluid, may not pass that degree.

The liquid mass is now introduced into bags of canvass, and submitted to the action of a press, by which the essentially liquid portion, which is very saccharine, is squeezed out; this liquid is kept in large vats, where it cools. The solid matter remaining in the bags is again placed in a vat, and treated with a fresh quantity of water at 114° Fahr., in the proportion of 111 gallons of water to 441 lbs. of residue. The mixture is stirred so as to form a porridge, which is re-introduced into the boiler, and heated to a temperature of 2010 Fahr., at which it is maintained for one hour. The mass is then pressed as before in bags of coarse canvass ; the liquid which filters is less saccharine than that obtained by the first operation, but it is rich in nitrogenous compounds, which form the base of the yeast. The liquors resulting from both operations are mixed together, and are exposed to the action of the air in large uncovered vats during two, three, and even for ten days, according to the external temperature.

This exposure to the air is one of the chief points in the new method. In order to set the liquid in fermentation, it is re-warmed to a temperature of 89.6o Fahr., and a small quantity of fresh yeast stirred up in a little warm water added. The fermentation sets in very soon, and may be conducted either in barrels or in vats, around which a temperature of 59° Fahr. should be maintained during the whole operation.

The yeast obtained by means of this process possesses the following properties:1. The raising power is much superior to that of all other yeast; 2. it has no bitter or acid taste, and consequently is admirably adapted for pastry work; and 3. it is of an extreme whiteness, and consequently does not require to be washedhence it preserves all its force.

The residue remaining after the fermentation may be employed to make vinegar. -Le Genie Industriel, June, 1854.

Natural Deposit of Saltpetre.-Prof. W. H. Ellet, of the United States, reports that there has been discovered in Bradford County, Pennsylvania, a regular vein of nitre, believed to be unique in its character. The nitre occurs as a solid and uncrystalline deposit in the horizontal seams of a sandstone rock, and in veins proceeding from them at different angles; and the rock itself, which is quite porous, is abundantly charged with the same material. The nitre itself is very pure, containing mere traces of nitrates of lime and magnesia. The sandstone in which it occurs is siliceous, containing a little carbonate of lime, and a notable quantity of silicate of potash.

ART. VI.-Bulletin of Industrial Statistics.

COMMERCE AND MANUFACTURES OF HOLLAND.

General Commerce. Some of our readers may, perhaps, ask why it is we devote so much space to statistics, especially of countries with which we have little or no communication. We shall anticipate the question, by stating that we are influenced by three causes:-1st, we believe that one of the first elements of success in modern commerce is a knowledge of its exact condition in every civilized country; 2nd, that it is of great importance for the people of a country to be reminded that there are many nations in existence besides themselves, and that frequently these nations are silently making a far greater relative progress than ourselves; and 3rd, that the efforts which many of these nations are making may serve as examples and stimulants to us. To Ireland, such a lesson ought to be especially valuable, and accordingly we shall select Holland on the present occasion, because it is small,