470 Mr. M. Carey Lea on the Transformations of 



lowest point for ordinates, and the observed distances through 

 which the telescope has been moved from its first position as 

 abscissae, we can construct the path of the axis of the pencil 

 through the liquid. 



A previous observation of different points on the scale, 

 before the liquid is poured into the vessel, gives the inclina- 

 tion of the telescope to the vertical, as in the first case. By 

 measuring the inclination to the vertical of the tangent to the 

 curve obtained, we can determine the refractive index at the 

 various points of the liquid. 



Assuming the curve for a short distance to be a straight 

 line, the index of refraction of the layer of liquid between 

 any two points can be calculated as in the first case, and a 

 similar formula will be true. 



XL VI. Transformations of Mechanical into Chemical Energy. 

 (Third Paper.) Action of Shearing-Stress (continued). 

 By M. Carey Lea. 



THAT mechanical energy may be transformed into chemical 

 has been, I believe 1 may say, well proved by the reac- 

 tions described in the previous papers of this series. But the 

 matter is one of sufficient importance to make it desirable to 

 accumulate evidence and to obtain a solid foundation of fact 

 on which to rest the argument. 



In the paper which described the effects of shearing-stress 

 (Phil. Mag. Jan. 1894) I was able to cite one instance 

 only in which the decomposition-product was obtained in 

 easily weighable quantities. More lately others have been 

 obtained, among them one, mercuric oxide, in which it can be 

 determined how many units (gram-metres) of mechanical 

 energy have been transformed into chemical. 



Silver oxide precipitated and dried in the absence of daylight 

 is soluble without residue in ammonia. After trituration, 

 therefore, the unchanged portion is easily removed by that 

 solvent. 



1. Half a gram of silver oxide wholly soluble in ammonia 

 was triturated for 20 minutes in a porcelain mortar, the un- 

 changed portion was removed by ammonia, the residue was 

 treated with nitric acid, filtered, and the silver thrown down 

 b}' hydrochloric acid. 



Silver chloride obtained. . . . *0402, 

 Corresponding to metallic silver . *0303. 



The use of a porcelain mortar is attended with the dis- 



