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BREAKING OF RAILWAY CAR AXLES.

A writer in the New York Journal of Commerce attributes the breaking of the axles of railroad cars to torsion, or twisting, occasioned in turning curves. He says that both wbeels are keyed, or otherwise fastened, on the axle; so that they must have a common velocity. In turning curves, the wheel on the outer rail must have a motion as much greater than the other as is due to the greater cirele which it traverses. The only way, therefore in which the equal speed of the two wheels can be attained, is by the sliding of that on the inner rail, so as to compensate for its diminished velocity. The sliding of the wheel operates to twist the axle, and it generally parts at its connection with the wheels. This seems to be owing to the whole leverage of the wheel, acting from its flange to the center, bearing on this point. The only effectual remedy for this evil, is some method of securing an independent motion to opposite wheels; at the same time taking the strain off the axle. This fact may afford a hint to the inventive genius of some of our mechanics.

In answer to this, a civil engineer in the Public Ledger of Philadelphia, says :“The writer is probably not aware that all railway wheels are conical, or in other words, they have a larger diameter near their flanges, than at the outside of their treads; and that, as the centrifugal force of the trains drives their flanges towards the exterior rail, their bearing diameter on that rail increases, and on the interior rail it decreases, so as to compensate for the difference in the length of the rails, and avoid the sliding alluded t). Engineers, knowing the radius of their curvatures, regulate the cone and play of their wheela to suit; and are well pleased with the practical working of the simple mathematical rules which they apply. The frequent reference I see made this subject, by those who arə evidently not familiar with railway mechanism, must be the excuse for this explanation, by a civil engineer.

RAILROADS IN SPAIN. The Spanish provincial correspondence and newspapers are full of accounts of railroads and projects of railroads, by means of which every province looks forward to have its resources developed and its riches increased. Cadiz hopes to see her fallen trade revive; Barcelona to drive even the English smuggling trade in cottons out of the market. The semi-official organ of the ministry avails itself of the enthusiasm awakened on the subject by representing the present ministry as the government, whose special mission it is to endow the country with these means of communication, which are expected to change the face of Spain, and put her on a level with the other nations of Europe.

RAILWAY ACCIDENTS IN GREAT BRITAIN, The usual return relating to railway acccidents for the half-year, ending 31st of December, 1851, has been printed. The number of passengers was 47,509,392. The number of persons killed was 113, and 264 injured. There were eight passengers killed and 213 injured, from causes beyond their own control; 9 passengers were killed and 14 injured owing to their own misconduct or want of caution; 30 servants of companies or of contractors were killed and 17 injured from causes beyond their own control; 32 servants of companies or of contractors were killed and il injured owing to their misconduct or want of caution; 33 trespassers and other persons, neither passengers nor servants of the companies were killed and 9 injured by crossing or walking on railways. There was one suicide. Tho length of railways open on the 30th of June, 1851, was 6,698 miles, and on the 1st of December last, 6,890 miles ; being an increase during the balf-year of 192 miles.

THE LONGEST TUNNEL IN THE WORLD. One of the longest, if not the longest tunnel in the world is now in a forward state of completion. It is situated in Hungary, and leads from the shores of the River Gran, not far from Zarnowitz, to the mines in the Schemnitzer Hills. It is two geographical or about ten English miles long. It is intended to answer the double purpose of a channel to drain off the water accumulating in the works, and a railway to transport the ore from the mines to the river.

JOURNAL OF MINING AND MANUFACTURES.

GOLD MINING IN CALIFORNIA. FREEMAN Hunt, Esq., Conductor Merchants' Magazine, New York :

Sir :-Gold is obtained in California from two sources--the placer diggings and the quartz rock. A large portion of that which has been exported from that State has been obtained from the placer diggings. This method has been prosecuted to such an extent and with so much industry and care, that the best placers have been explored, and digging in the sand and banks of the streams has become much less profitable than at first. The consequence is that the attention of the gold seekers is more strongly attracted to the rock mining, which has been prosecuted to some extent, but in a far more limited degree than the diggings in placers.

In quartz mining, the gold is found penetrating the rock like veins, and to obtain it the rock must be crushed to a powder which is washed and the gold finally separated from the dust by mixing it with quicksilver.

There are two important points in this process. The first is, to crush the rock, and the second to obtain all the gold by the use of the quicksilver.

The first machinery for crushing quartz rock was put up in June and commenced work in July, 1851, on the big Mariposa vein. This was a Chilian mill and was put up by Messrs. Cook & Jackson; it crushed about five hundred pounds in twelve hours. The amalgam was examined once in three or four days and the yield found to be $250. to $375. The Chilian mills have proved to turn out more gold to a pound of the same ore, but they have failed entirely because they crush such a small amount in a day. In this respect they are only one step in advance of common hand mortare. This same company in August went another step in advance by puting up “ Stockton Stamps,” and set them in motion in September. These stamps weighed 209 pounds and were worked by a steam-engine. But they were too light. They would crush only two and-a-half tons in twenty.four hours. These light stamps were sent out to California under the impression that the rock would yield $2 00 or $3 00 in gold to the pound.

Stockton & Aspinwall's mill went into operation on the same vein in November, 1850. It contained twelve stamps weighing each 169 pounds. Their mine was por and the only part of their claims which worked to a profit was 120 feet on the Mariposa vein, and the rock from this they were obliged to transport to the mill at an expense of one cent per pound, and the amount crushed was only 3,500 pounds in twelve hours. Of course this would not pay. It was the assertion of the agent of this company that if the machinery had been heavier they would have succeeded. And this is probable, for the miners are now in the habit of bringing the rock to the mills and paying from $20 00 to $30 00 per ton for crushing it; which is an evidence that it is profitable.

All these first mills used the bowls with a single shaking table for separating the gold from the pulverized dust, by which about 15-16 of it ran off and only 1-16 passed through the shaking table.

These mills were originally designed for the gold mines of Virginia and Georgia, where they may have been very successful; but they were, unfortunately, found entirely unsuitable, under the circunstances, for California. They were generally driven by an engine of eight or ten horse power and, therefore, were competent to crush four or five tons of rock in a day. Such a mill, at Virginia prices for labor, could be worked at an expense of fifty dollars per day. If we suppose the yield to be one cent per pound, for five tons, it would amount to two hundred dollars per day, or one hundred and fifty dollars net profit in Virginia,

In California, on the other hand, the wages of the same number of laborers, or force, which was employed in Virginia, would amount to $274 per day, which would not pay expenses by $174. At two cents of gold to the pound of rock, the yield is only $400, which is a very insignificant return for California.

By contrasting this method of labor with that adopted by the successful mills, the importance of suitable machinery will be readily apprehended.

The Grass Valley Quartz Mining Company's Mill has been regarded as the “Model

Mill,” in California, as, in its success, it has been one of the most prosperous. This mill has thus far crushed the rock upon the old fashioned method long in use among miners, and known as “ stampers." Their form is somewhat modified and much larger on the face than usual. There are ten of them in the mill weighing each about 700 pounds, and they crush from thirty to forty tons of ore.per day. This at a yield of two cents to the pound is $1,600 per day, and supposing only two hundred work. ing days in a year, amounts to $320,000. But this inill has actually yielded on some days $3,800. Its average, however, is $70 to the ton or 31 cents to the pound. The quartz, even under the imperfect method of separating the gold with quicksilver, has yielded at this mill an average of three-and-a-half cerits to the pound of rock. This mill paid its original cost in sixty days after it was constructed : subsequently it has paid large profits, notwithstanding it has been three times remodeled, improved and enlarged. In the months of April and May alone the net profits of this mill exceeded $17,800, and the last arrival brings a statement of equal richuess in the yield. The highest estimate of expenses for running a mill of this kind is in round numbers about $400 per day.

There is one point in connection with quartz mining in California which has defeated many enterprising persons and caused the loss of capital also. It is that lack of experience which is necessary to command success in all mining operations. Many have attempted it who possess little or no real knowledge of mining; many aleo bave embarked in it without the necessary capital and have not been able to sustain themselves until abundant proceeds could be realized from the mine. All have been in error in relation to the suitable machinery.

The method of separating the gold from the pulverized quartz bas been very imperfect, and in some cases not more than one-half or one-third of it is obtained, as was proved by assaying it afterwards. Of course, this has been an unexpected difficulty to many. But it has now been to a considerable extent obviated by improved amalgamators, and will doubtless be still further remedied bereafter.

The extent of the quartz veins is estimated by Prof. Blake to be comprised" within a belt of land ten miles broad and running the whole length of the country north and south, and doubtless furnishing a supply of gold which it will take centuries to exhaust.” He also says “there can be no doubt but that quartz mining is destined to be the most permanent source of gold in this country. It will not be many years before it will attract that attention which, as an investment for capital, it evidently deserves.

J. T.

THE MANUFACTURE OF GLASS. We commence in the present number of the Merchants' Magazine the publication of a series of papers on the manufacture of glass. These cannot fail to be acceptable to our readers, as they will contain much valuable information relating to the discovery of the materials and their various improvements, which, under the influence of heat, are fused into a substance long known as the beautiful, pellucid glass, so indispensable in domestic, chemical, building, and various other uses. The process through which its manufacture bas reached its present state of perfection, with statistical and other valuable knowledge of the art of glass making will be embodied in these articles. To say they are from the pen of Deming Jarvis, Esq., the well known founder and principal of the Boston and Sandwich Glass Manufactory, in Sandwich, Mass., is sufficient assurance to all who know this gentleman that they will be reliable and interesting

THE MANUFACTURE OF GLASS.NO. I.

It may be safely asserted, that no department of art has from its earliest period attracted so much attention and investigation, none involved so extensive a range of inquiry, or been productive of more ingenious, interesting, and beautiful results, Than the manufacture of glass.

The question of the origin of glaes goes back to the remotest antiquity, and is involved in almost entire obscurity. All that modern writers on the subject are enabled to do, is to glean hints and indistinct statements in reference to the subject; from the very brief and unsatisfactory accounts of the ancients. There, howerer, throw but a feeble light upon the precise point of the origin of the manufacture; and little is proved beyoud the fact of its great antiquity.

That the subject held a very prominent place in the technological literature of the ancients, is clearly proved-Pliny, Theophrastus, Strabo, Petronius, Arbiter, Berzelias, Neri, Merrit, Runket, and others, referring constantly to it. The writings of all these demonstrate the deep interest existing upon the subject at their various times; but still fail to present us with any connec ed or detailed account of the rise and progress of the art.

When it is considered that the elements involved in the manufacture of glass are derived from the earth, -not one of its components being in itself transparent, but earthy, opaque, and apparently incapable of being transmuted into a transparent and brilliant substance, when it is considered that from these a material is produced almost rivaling the diamond in luster and refractive power, and sometimes so closely resembling the richest gems as to detract from the value of the costliest.--can it be wonderful that in the earliest ages the art was invested with a mysterious interest attaching to no other mechanical department ?

From the earliest periods, up to the eighteenth century, the art, from the peculiar knowledge and skill involved, could only minister to the wants or pleasures of the luxurious rich. The rarity of the material rendered the articles greatly valuable, as tasteful ornaments of dress or furniture ;-indeed, it is well known that the glass of Venice, at one period, was as highly valued as is plate of the present day; and the passion for possessing specimens, promised in England at least, to excite a spirit of speculation fully rivaling that exhibited in the tulip mania, so ridiculous, as well as ruinous, in Holland.

It has been reserved for the present age, however, to reuder the art of glass making tributary to the comfort of man-to the improvement of science—and by its moderate cost, to enable the poorest and humblest to introduce the light and warmth of the sun within, while excluding the storms and chilly blasts ; to decorate his table with the useful, and minister to his taste, at a cost barely more than that of one of his ordinary days' labor. That which once was prized and displayed as the treasure and inheritance of the wealthy, and which with sacred carefulness was handed down as of precious value, may now be found in the humblest dwellings, and is procured at a charge which makes the account of the former costliness of glass to partake almost of the character of the fabulous and visionary.

That the art of glass manufacture is destined to greater progress and higher triumphs, cannot for a moment be doubted; and the time will arrive when, from increased purity of materials and progressive chemical development, the present position of the art will fall comparatively into the shade. It is no undue stretch of the imagination to conceive that lenses shall be perfected, whose 'purity will enable the astronomer to penetrate the remotest region of space; new worlds may perhaps be revealed, realizing all that the “ moon hoax” promised

"The spacious firmament on high,

With all the blue, etherial sky

And spangled heavens be read as a book, and man perhaps recognize man in other worlds than his own. It may be that in its triumphs it is destined to concentrate the rays of the sunlight, and make the eye to pierce into the secrets and deep places of the sea,

" Full many a fathom deep." Man may be enabled to read the wonders and the hidden works of the Almighty ;it may be, that the power of the traditional lens of Archimedes upon the fleet of Mar. cellus shall be realized, in the absorbing and igniting, and perhaps useful power of some feature of its progress; and in its sphere, the art become fruitful in practical results, rivaling the highest attainments in the department of scientific progress. It is a visionary speculation to believe, that by the aid of machinery it may be readily rolled into sheets, as is iron or lead now in use. It will minister more and more to the necessities and comfort of mankind, and contribute largely to the many and various manufacturing purposes of the age. That its practical adaptations are not already known or exhausted, cannot be doubted; and its applicability in some cheaper form for vessels of large size and certain shape, and (strange as it may seem) for tesselated and ordinary flooring and pavements, are among the results which we think yet to be demonstrated in its progress.

An elegant writer in a late number of Harper's Magazine says :“The importance of glass, and the infinite variety of objects to which it is applicable, cannot be exaggerated; indeed, it would be extremely difficult to ennumerate its

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properties, or estimate adequately its value. This, then, transparent substance, so light and fragile, is one of the most essential ministers of science and philosophy, and enters so minutely into the concerns of life, that it has become indispensible to the daily routine of our business, our wants, and our pleasures. It admits the sun and excludes the wind, answering the double purpose of transmitting light and preserving warmth; it carries the eye of the astronomer to the remotest region of space ;through the lenses of the microscope it develops new worlds of vitality, which without its help must have been but imperfectly known; it renews the sight of the old, and assists the curiosity of the young; it empowers the mariner to descry distant ships, and trace far off shores—the watchman on the cliff to detect the operations of hostile fleets and midnight contrabandists, and the lounger in the opera to make the tour of the circles from his stall; it preserves the light of the beacon from the rush of the tempest, and softens the flane of the lamp upon our tables ; it supplies the revel with those charming vessels in whose bright depths we enjoy the color as well as flavor of our wine; it protects the dial whose movements it reveals; it enables the student to penetrate the wonders of nature, and the beauty to survey the marvels of her persoo; it reflects, magnifies, and diminishes—as a medium of light and observation its uses are without limit, and as an article of mere embellishment, there is no form into which it may not be molded, or no object of luxury to which it may not be adapted.”

In contrast with the foregoing, we will make one more extract from an English writer of ancient date. Halinshed, in his “ Chronicles," priblished during the reign of Elizabeth, says:

" It is a world to see in these our days, wherein gold and silver aboundeth, that our gentility, as loathing these metals, (because of the plenty.) do pow generally choose rather the Venice Glasses, both for our wine and beer, than any of these metals, or stove, wherein before time we have been accustomed to drink; but such is the nature of man generally, that it most coveteth things difficult to be attained-and such is the cötimation of this stuff, that many become rich only with therein new trade into Murana, (a town near to Venice,) from whence the very best are daily to be had, and such as for beauty do well near match the Crystal or the ancient Murrhina Vase, whereof now no man has knowledge. And as this is seen in the gentility, so in the wealthy commonality the like desire of glasses is not neglected, whereby the gain gotten by their purchase is much more increased, to the benefit of the merchant. The poorest endeavor to have glasses also if they may; but as the Venetian is somewhat too dear for them, they content themselves with such as are made at home of fern and burnt stone ; but in fine, all go one way, that is to the shades, at last."

PROPERTIES OF GLASS.

Glass has properties peculiarly its own-one of which is that it is of no greater bulk when hot, or in the melted state, than when cold. Some writers state that it is (contrary to the analogy of all other metals) of greater bulk when cold than when hot.

It is transparent in itself, but the materials of which it is composed are opaque. It is not malleable-but in ductility ranks next to gold. Its flexibility, also, is so great that when hot it can be drawn out like elastic thread miles in length in a moment, and to a minuteness equal to that of the silk wor... Brittle, also, to a proverb, it is so elastic that it can be blown to a gauze like thinness, so as easily to float upon the air. Its elasticity is also shown by the fact that a globe, hermetically sealed, if dropped upon a pulished anvil, will recoil two-thirds the distance of its fall, and remain entire until the second or third rebound. (The force with which solid balls strike each other may be estimated at ten, and the reaction by reason of the elastic property at nine.) Vessels, ealled bursting.glasses, are made of sufficient strength to be drawn about a floor; a bullet may be dropped into one without fracture of the glass ;-even the stroke of a mallet sufficiently heavy to drive a nail, has failed to break such glasses. In a word, ordinary blows fail to produce an impression upon articles of this kind. If, however, a piece of flint, cornelian, diamond, or other hard stone, fall into one of these glasses, or be shaken therein a few moments, the vessel will fly into a myriad of pieces.

Glass of the class called Prince Rupert drops, exhibits another striking property. Let the small point be broker, and the whole flies with a shock into powder. ters have endeavored to solvethe philosophy of this phenomenon---some

by attributing it to percussion putting in motion some subtile fluid with which the essential substance of glass is permeated, and thus the attraction of cohesion being overcome. Some deVOL. XXVII-NO, III,

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