92 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



melted by a jet of coal-gas and oxygen, and cast into an 

 ino;ot. Five ingots thus made were cut into small fraff- 

 ments by hydraulic pressure, melted together and kept in 

 fusion for a long time, and then poured into a single ingot. 

 This was forged and rolled into bars, which were then 

 fused in rectangular troughs. After forging, the metal ap- 

 peared homogeneous, and gave a bar 35 centimeters long, 

 7.5 wide, and 2.5 thick, the density of which at was 

 21.522. A third was cut off, and the other two thirds 

 a^ain forged into a bar 95 centimeters lon<^, 2.5 centim- 

 eters wide, and 2 centimeters thick, having a density of 

 21.648. This was rolled between polished rolls nearly to 

 the dimensions required, 4.1 meters long, 2.1 centimeters 

 wide, and 5 millimeters thick, and then finished by passing 

 it through a steel draw-plate. During all these rolling op- 

 erations it was repeatedly annealed. In some remarks on 

 this paper, H. Sainte-Claire Deville gave the results of his 

 analysis of this alloy. He found 89.42 of platinum, 10.22 of 

 iridium, 0.16 of rhodium, 0.10 of ruthenium, and 0.06 of iron. 

 The density calculated from this composition is 21.51 ; that 

 actually observed by him, 21.515. The third cut off of the 

 bar above mentioned has been made by Deville into two 

 tubes more than a meter long, closed at both ends, one of 

 which has a capacity of more than a liter, designed for the 

 determination of boiling-points. Both tubes carry marks 

 exactly one meter apart. One of them communicates by 

 means of a capillary tube with a Regnault manometer, and 

 acts as an air thermometer; the pressure being determined 

 by the manometer and the temperature by the elongation 

 of the tube, compared with its fellow kept in ice, the expan- 

 sion-coefficient being known. 



MECHANICS. 



1. Of Solids. 



In Mechanics, Tschechowitsch has described a universal 

 apparatus for illustrating the elementary laws of mechanics 

 in class instruction. By its means the parallelogram of 

 forces, resolution and composition of forces, the action of 

 parallel and of oblique forces, action and reaction, the prin- 

 ciples of the lever and of the balance, can be very fully de- 



