176 On Compounds of Ethylene. 
tails of comets* (query: portions of very elliptic rings, the plane of 
ART. XV IiL—On some Compounds of Ethylene; by H.S. Burr. 
{Communicated to this Journal by A. W. Horrman, Ph.D. }t 
Amone the hydrocarbons which are capable of replacing hy- 
drogen, the radicals of the general formula CnH(n+1) we, the 
homologues of ethyl, are best examined. There is another class 
of hydrocarbons a is may be represented by the general form- 
ula CnH(n—1). The only vel known term of this series 
is the radical allyl CeHs to which the attention of chemists has 
been especially called of late by the researches of Messrs. Hoft- 
mann and Cahours on allylic alcohol. These researches lave 
the great comet of 1680, immediately after its perihelion passag? 
v 20,000,000 
Herschell’s Outlines of Astronomy. 
+ From the Proceedings of the Royal Society, received June 10, 1856. Read 
the 19th June, 1856, ‘ y Die ae 
