430 Mr. J. A. Phillips's Notes on the Chemical Geology 



In addition to the substances above enumerated minute traces 

 of iodine were found, but in such small proportions that its pre- 

 sence could only be detected when large quantities of water were 

 operated on. 



As the samples employed for analysishad, before being brought 

 to this country, been concentrated by boiling, it is evident a loss 

 of carbonic acid would have taken place had any admixture of 

 scsquicarbonate been present. 



The incrustations, which at certain seasons of the year are 

 found to the extent of hundreds of tons on the lake-shores, 

 chiefly consist of carbonates of soda in which the proportion of 

 sesquicarbonate is variable; and specimens were examined in 

 which monocarbonate only was present. Besides the carbonates 

 of soda, these deposits contain 3 per cent, of chloride of sodium 

 and about 5 per cent, of sulphate of soda, together with a trace 

 (0*22 per cent.) of silica. 



Summary. 



The following are some of the more important facts observed 

 on a careful examination of the gold-regions : — 



(1) The quartz veins of California almost uniformly exhibit 

 evidences of having been formed by successive siliceous deposits 

 parallel to the walls of the enclosing fissure ; and when fragments 

 of exfoliated slaty rock become enclosed, their planes are usually 

 parallel to those of the quartz in which they are imbedded. 



(2) All remuneratively productive gold veins contain notable 

 quantities of iron pyrites and other metallic sulphides ; and the 

 association of these bodies is so constant and remarkable, that 

 it is probably the result of some chemical action regulating the 

 distribution of the precious metal. 



(3) The auriferous quartz of the Pacific gold-fields invariably 

 contains a certain quantity of potash together with a small amount 

 of water which is not eliminated at a temperature of 212° F. 

 Under the microscope it only exhibits well-defined fluid-cavities 

 in specimens that are more than usually crystalline ; and these, 

 even in the same crystal, when heated, become full at by no 

 means uniform temperatures. 



(4) Mineral veins of evidently very recent date are met with 

 in various localities on the Pacific coast ; and some of these con- 

 tain both gold and silver. 



(5) In addition to the gold found in quartz veins, this metal 

 occurs in certain bands of metamorphosed slates. The outcrops 

 of these, like those of ordinary veins, are frequently coloured red 

 or brown by the decomposition of pyrites. 



(6) The old Tertiary river-beds constituting the deep diggings, 

 and frequently overlain by a volcanic capping, contain large 



