436 H S. kSionmers : 



(c) Mtteoritir Origin.- - 



Before discussing what bearing the chemical composition of 

 the obsidianites has to the meteoritic hypothesis of their origin, 

 some accoimt of their distribution from a chemical standpoint 

 is necessary. 



Referring back to the table of analyses, it will be seen that 

 the specific gravity practically varies inversely as the percentage 

 of silica. By determining the specific gravity of a specimen, 

 therefore, we have a quick method of arriving at its approxi- 

 mate composition. On receiving Mr. Ampt's analysis of the 

 Peake Station obsidianite, I was struck by the extremely low 

 specific gravity (2.385) of this specimen, no other recorded 

 determination being less tlian 2.41. I therefore set to work 

 to carefully determine the gravity of some of the specimens at 

 my disposal. All buttons were cai-efully cleaned and scrubbed 

 with dilute hydrochloric acid, and after being washed and dried, 

 were weighed on a chemical balance. They were then boiled in 

 distilled water to get rid of every trace of surface air bubble, 

 and on cooling were re-weighed in water. Six determinations 

 were uuide of buttons from Hamilton, from Balmoral, and from 

 Peake Station. The results are given l)elow. together with six 

 specific gravities recorded by Mr. Simpson of obsidinnites from 

 Kaltroorlie. 



I. — Six suuill specimens from near Hamilton. 



II. — Six small specimens from Balmoral. 



III. — Six large specimens from Lake Eyre District. 



IV.- Six spei'iuieus from Kalgoorlie. 



Mr. Kerr (iraiit determined the bulk specific gravity of sixty- 

 nine si)Ccimeus from the Jjake Eyre District, and kindly fur- 

 nished me with the result obtained, am/.., 2.395. 



The above results are extremely interesting, as they point to 



