302 Proceedings of the Royal Irish Academy. 



The most probable values of the constants of CHj are 



^^2 = ^ = - I ^ = 12, 



u)"2 = 1-9600, il"JB = 0-9600, 

 r" = 1. 



The most probable values of the constants of CH are 



m, = -5, (3 = 12, 



/ = 1-1081, 0)'- = M175, 



co'V = 1-2356, //3 = 1-7727. 



Silicon-tetrahydride (SiH4). — One atom of silicon is capable of 

 forming a gas with four atoms of hydrogen, and this gas has much in 

 common with marsh gas, silicon replacing carbon. 



Its most probable constants are 



Mi = 



1 - 1-> 

 8 



-3, 





ft = 



28, 



co'^- = 



1-7778, 





/^ 



"(3 = 



-2-0506, 



r" = 



1. 











The most probable constants of 



(SiHs) 



are 





Ms = 



8-/3 

 6 



25 





/3 = 



28, 



0)""- = 1-5375, fi"'l3 = - 0-7719, 



r'" = 1. 

 The most probable constants of (SiHj) are 



^2 = -J- = - y /3 = 28, 



w"2 = 1-3313, A*"/? = +0-3313, 



r" = 1. 



