1884.] The Index of Refraction of Liquefied Gases. 191 



The result has been a mechanism which consists of two distinct 

 features : 



(1.) A mechanical principle, by which an arrangement of spheres 

 and rollers is made capable of transmitting motion, which can be 

 independently varied in any required manner. 



(2.) The arrangement by which mathematical results can be at 

 once obtained with any required numerical quantities, however large. 



The rest of the paper consists in a discussion of these principles, 

 and of the practical applications which, beside enabling the operations 

 already mentioned to be performed, enable logarithms and roots to be 

 calculated, besides giving a convenient computator for reducing 

 tables of result*. 



The almost entire absence of friction enables a chain of spheres and 

 rollers to be employed in a very compact form and with accurate 

 result. Thus, with two sets, the moment of an area, the integration 

 of volumes, &c., can be obtained ; with three, the moment of inertia, 

 and other results. In fact, the operation 



can be performed with n sets of the fundamental form of mechanism. 

 By using the screw arrangement, the value of a ratio or differential 

 coefficient can be obtained ; and, by using two sets, the second dif- 

 ferential coefficient, or 



d~s 



- = acceleration, 



or rate of change of velocity, is given. By using the integrating and 

 differentiating mechanism in conjunction, rate of working, or H. P. 

 can be indicated on a dial. 



Various practical applications, such as a planimeter, a sliding rule 

 for giving at once A, M, and I, a H. P. indicator are shown. Finally, 

 the application of the mechanism to the transmission of power is con- 

 sidered, as well as the mechanics of problem, and a modification of an 

 important nature for the roller bearings is described and illustrated. 



XVIII. " On the Experimental Determination of the Index of 

 Refraction of Liquefied Gases." By Dr. L. BLEEKRODE. 

 Communicated by Dr. GLADSTONE, F.R.S. Received 

 June 19, 1884. 



[Publication deferred.] 



The Society adjourned over the Long Vacation to Thursday, 

 November 20th. 



