568 TRANSACTIONS OF T^E AMERICAN INSTITUTE. 



ical composition as physical properties, and wc are forced to the 

 conclusion that the different volatile constituents of pure petro- 

 leum are nothing but the members of the well known series 

 of the homolognes of marsh gas, of which the general formula 

 is Cn Hn -f- 2 ^^" I'^ther Cn Hn + 1, H, in which n may represent 

 an}^ number, as will be clear from the following table, to w^hich 

 ♦ are added the new names, according to Prof. Tillman's system, in 

 which the atomic w^eight of carbon is 12, and is represented by 

 either c or r. One atom of hydrogen is denoted by «7, and two 

 atoms by either el or ah; thus Cg Hg •'according to the old nota- 

 tion is expressed by ach, and all its multiples a diflereut vowel 

 prefix. 



