794 Transactions of the American Institute. 



more of sugar is extracted than by the old bone-black process, and 

 the general adoption of the parchment paper plan would immensely 

 increase the production of the article. The total amount of sugar 

 manufactured annually is not less than 2,800,000 tons. It is 

 obtained principally from four different sources, in about tho 

 following proportions: 



Sugar cane 2,000,000 tons, or 71.42 



Beet 630,000 tons, or 22.50 



Palm 140,000 tons, or 5.00 



Maple 30,000 tons, or 1.08 



MECHANICAL PROPERTIES OF STEEL. 



William Fairbairn, F. R. S., communicated to the British Asso- 

 ciation the results of a laborious series of experiments to determine 

 the comparative merits of different kinds of steel as regards their 

 powers of resistance to transverse, tensile and compressed strain. 

 [n order to arrive at correct results, he applied to nine of the first 

 manufacturing firms, including Bessemer & Co., for the fifty-two 

 ijpecimens experimented upon. The experiments commenced with 

 the transverse strains, which were conducted, as on former occa- 

 sions, by suspending dead weights from the middle of the bar, 

 which was supported at its extremities, the supports being four feet 

 six inches apart. Immediately over the center of the bar, at a 

 point equidistant from the supports, a wheel and screw Avas attached 

 to a scale, on which the weights were placed, fifty-six pounds at a 

 time. After each weight laid on, the deflection was taken, and the 

 experiment was continued until a permanent set was obtained. The 

 permanent set was observed at intervals in the following manner: 

 After the deflection produced by the load had been ascertained, the 

 screw was turned so as to raise the scale and relieve the bar of the 

 load, thus enabling the experimenter to ascertain the efl'ects of 

 the load upon the bar and register of the permanent set. The 

 results of the experiments on transverse strains show that within 

 the elastic limits the deflections are in proportion to the pressures. 

 The bars generally exhibited very high powers of resistance to 

 transverse strain, the mean value of the unit of working strength 

 being six tons. It was next shown that taking eleven tons per 

 square inch as the mean value of the compressive and tensile resist- 

 ance of wrought iron at the elastic limit, the value of the unit of 

 working strength is less than two tons, and thence it followed that 

 the transverse strength of these steel bars will be about three and 



