84 ANNUAL OP SCIENTIFIC DISCOVERY. 



revolution about the edge of the block. Another tenth was added, and 

 another division obtained : and so on, until all five divisions were marked. 

 The length of the divisions being about one-fourth of an inch, they were 

 very readily subdivided into ten equal parts, which gave me immediately 



i _ths of a milligram. The weight of any quantity of matter less than 

 one-half milligram may be now estimated to T ^th of a milligram by 

 placing it on the pan and observing the deflection. 



For the thousandths, still more care and patience is required, the filament 

 being much finer and somewhat shorter, and the pith disc smaller and as 

 thin as possible. In order to obtain the primary graduations of hundredths, 

 one of the above pieces of hair, equal to ^fh. milligram, is divided into ten 

 equal parts, which gives us weights of y^th milligram. The deflections 



caused by these weights, divided into ten equal parts, give j^Vu tn of> a 

 milligram. 



As the least breath of air interferes with the graduations and weighing, 

 the whole instrument is protected by a glass case, the end of the case next 

 the graduated arc being on a hinge. 



In elastic rods of square section, the deflection is proportional to the 

 weight; in those of circular section this law is slightly departed from; but 

 by the above method of ascertaining directly the value of each division, the 

 error is avoided. Silliman's Journal. 



IMPROVEMENTS IN MILITARY IMPLEMENTS. 



Novel Field Artillery. General Sir Charles Shaw, of England, has recently 

 perfected a novel piece of field artillery, from which he anticipates extra- 

 ordinary results in the percentage of destructiveness and economy of 

 expenditure. Napoleon's axiom was that to bring a continuous concen- 

 trated fire upon a given point of the enemy's position was the secret of 

 victory. Animated by this idea, the general has turned his attention to the 

 construction of a machine which shall accomplish this object with the least 

 amount of risk to the party using it. The invention may be briefly described 

 as an ambulatory infernal machine, based upon the Fieschi model. It con- 

 sists of a row of twenty-four rifle barrels, bound together, fitted to an axle, and 

 mounted upon a pair of strong, light wheels. The axle is capable of depres- 

 sion or elevation to any angle within a radius of fifty-five degrees, so that 

 the necessary elevation according to the distance of the enemy may be 

 insured. The barrels may be either breach-loading, upon the revolver prin- 

 ciple, or they may, as in the model exhibited, be charged in the ordinary 

 way, at the mouth, and rammed down, and all may be discharged at a single 

 fire, or in four divisions of six each. The whole machine is but 200 pounds 

 weight, and is sufficiently portable to be moved about, turned to the right or 

 to the left, and its fire directed with certainty by a single soldier while with 

 its ammunition-cart, containing a relay of barrels and an ample supply of 

 cartridges, it may be moved from one part of the field to another by a 

 single horse at a handgallop. The general affirms that one of these field- 

 pieces, which may be served effectually by eight men, alloAving for casual- 

 tics, will throw in a more deadly fire than a body of 200 infantry armed with 

 the best description of rifles in existence, and that the ratio of its destruc- 

 tiveuess, as compared with ordinary infantry firing in line, is as seventy-five 



