202 HAWAIIAN ISLANDS. 
occurrence of siliceous deposits and hyalite from decomposing vol- 
canic rocks and trachyte has often been noticed.* 
The following are the results of chemical examinations made for 
this report by Prof. B. Silliman, Jr., with respect to several of the 
salts of the volcano. 
1. Sal ammoniac containing a large per-centage of iron. 
Chlorid of ammonium - - - - - 65°53 
Protochlorid of iron - - - - - 12°14 
Peroxyd of iron - - - - - - 8°10 
Chlorid of aluminium - : - : : 13:00 
Insoluble matter and loss” - - - - - 1:23 
This sal ammoniac becomes of a rusty colour after exposure. 
2. Blue sulphate of copper. 
Sulphuric acid : - - - : - 37°97 
Soda - - - - - - - 16°80 
Oxyd of copper - - - - - - 10°80 
Alumina and iron - - - - - - 5:00 
Manganese > 2 5 z < > 4:00 
Chlorine and potash - - - - - Trace 
Insoluble silica : - - - - - 21:00 
Sulphur and loss - - : = : 4:43 
A selected sample of the purest salt yielded in a chlorid of calcium 
apparatus 19-99 per cent. of water. The salt analyzed was evidently 
a mixed sulphate of soda, alumina, and copper. Ten grains were 
employed in the analysis. 
Green salt of copper.—This occurs as a thin incrustation with the 
gypsum, alum, and other salts of the sulphur bank. The quantity 
was too small fora complete analysis. From the examinations made, 
it appeared to be a simple sulphate of copper mixed with sulphate 
of lime. 
Iron alum.—Consists principally of the sulphate of alumina, with 
the sulphate of peroxyd of iron, sulphate of soda, traces of chlorine, 
besides the usual amount of water. 
* Humboldt states that M. Cordier first made known the siliceous and opal formations 
from the decomposition of lavas by sulphuric acid.— Pers. Nar., Eng. trans., i. 175. 
See also Breislak, Introd. alla Geologie, ii. 238; Beudant, Voyage Min., iii. 507; Darwin, 
Volcanic Islands, pp. 24 and 34. 
