Page:Science vol. 5.djvu/260

 iVot. v., Ho. 111.

��reituctJoii. Copper i« Gliding new and important appUcations in Lhe new alloys, phoapbcir-bronze, mnnganesc-hrunze, and other compositions.

The working of heavy raasseB is demanding the co[iatruction of larger hammers; and it is becoming seen tbat light steam-ljaniiners are aclually injurious to the parts foiled by them. Testing-machines are now In dally use, in the hands of the engineflr, to determine the exact valne of the metals proposed for use in his designs, and to exhibit the strength of completed members.

In bridge-construction, the St. Louis bridge was a novel departure in the use of steel In compression ; and the New-York and Brooklyn bridge is an equally BUfcesaful example of application of wires for sus- pension over long spans. The new bridge Forth exhibits still another modern novelty in its great cantilevers, the onJy known expedients for success- fully spanning seventeen htiiidrcd feet with a rigid structure. In rail- road and canal construction, the ri- valry between the two aystems of transportation is beat lIluatrBted by the enormous canals, now in progress and proposed, to conned ocean with ocean, and sea with sea, and, as in the case of the Manchester sh I p-canai, to take ocean-going ships into the Interior of the country. This led lo the study of harbor-construction, and reference to Hie methods of mak- ing and handling blocks of maeonry weighing three hundred and fifty tons each, in tho building of their sea- walls. A new and great improvement in the methods of supply of air for respiration, to the workmen sent into the depths during the operations just referred to, is that of absorption of exhalc!d carbonic acid by a basic salt, and the introduction of oxygen from under compression in small tanhs carried by the diver, who is thus enabled under water for considerable periods of tunnelling in red sandstone, a speed of from ten to fourteen yanls perday Is attained, and of twenty-four yards in chalk. Dynamil* and tunnelling machines are making this great progress possible.

Progress in motors has not been rapid during tale years. The beat of recent double-cylinder non-con- densing steam-engines demand but two jwunds and seven-tenths of coal per horse-power and per hour; wbile the condensing-engine has worked down to about a pound and a half. The gas-engine is gradu- ally coming forward as a rival of the st«am-engine in small powers; its greater safety, and the reduction of current expenses in various directions, giving it a superiority in some respects. Water-wheels have attained an efQclency of eighty-flve per cent; and the turbine, with Its high efficiency, offers great advan- tJ^(es In application where the fall is low, or the variation of height of tail-water considerable. In

��n of power, the introduction of water, steam, aud compresed air, sent out from a cciilnl station, is a promising direction of progress.

��COFFINS OF THE SEVENTH CENTURY'

W1111.E digging a trench recently in the rue Salaodt in Paris, an ancient burial-ground was encountered. The discovery was made among the rubbish and > ruined walls ot the old Gallo-Romaii outskirts a" depth of about one and ona-half metres. Ninet« coffins made of plaster, and four or five of s

t interesting things exhumed. The full e tent of the burial-ground could not be delcnnlnc^ because it extends beneath some houses, 'niat il

���tbe sepultures belonged to Christians id probata from the fact that they invariably pointed toward tl cast, and by the Christian symbols. The coffins b longed lo the seventh, eighth, and ninth centuries. Previous to this period they had been mode of atone, but those ot the epoch underconsideration are mostly of plaster. The coffins all had the shape of an eloaT|^ gated trapezoid, being narrower at the foot, and w found flile<l with dirt, the covers having given w The piaster sarcophagi are not unique, since two thousand have already been reported as f( Figures are usually imprinted upon the e the heail and foot, but not more than one or t» a hundred are ornamented on the long side. cross emblem of Christianity, inscribed in a < symholical of eternity, Is the predominant form < ornamentation. There are numerous other c tations, but it is difficult to classify them, or to undcg stand their signiflcation.

' Abrid^froiB Sclenct a naltm.

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