440 



That these oscillations must exist will be evident, when it is con- 

 sidered that the gyroscope, with the weight attached and the disc 

 not spinning, becomes an ordinary pendulum : the effect of the 

 spinning being to disturb its oscillations, and to lessen their extent 

 to an unlimited amount, whenever the spinning of the disc is suffi- 

 ciently rapid. 



The preceding investigations, as well as the experiments, show 

 that whenever a force is applied to the axis of a revolving disc, more 

 or less of the momentum due to this force is converted into a mo- 

 mentum of rotation parallel to a plane which is perpendicular to 

 that in which the force acts. 



April 2, 1857. 



The LORD WROTTESLEY, President, in the Chair. 



The following communications were read : 



I. " Researches on Silica." By Colonel PHILIP YORKE, F.R.S. 

 Received March 25, 1857. 



(Abstract.) 



This communication is principally devoted to an attempt to de- 

 termine the formula of silica, and to the relation of some remarkable 

 results obtained in this research. After giving some account of the 

 grounds on which the three different formulas now in use among 

 chemists (viz. SiO 3 , SiO 2 , and SiO) had been advocated, the author 

 proceeds to state, that it appeared to him that the direct method 

 which had been followed by Rose deserved the preference. This 

 method consists in determining the quantity of carbonic acid which 

 is displaced from excess of an alkaline carbonate in fusion, by a given 



