2 THE "iron blow" AT THE LINDA GOLDFIELD. 



to the West Coast. Thus, on the whole, a settled and 

 reliable opinion as to the causes governing the past geological 

 history of the "Iron Blow," accounted for by Mr. Johnston 

 as a process of deconip)Osition of materials at hand, in opposi- 

 tion to the theory of volcanic agencies which I have advanced 

 in my report, deserves to be treated in detail, as involving 

 important issues. 



Decomposition is, I believe, a chemical process by which 

 the destruction of one or more substances leads to the sub- 

 stitution and depositing of quite different matters, thereby 

 bringing about the rearrangement of the former original 

 substances in quite different forms. 



In this case it has been attempted to be proved that those 

 massive beds of pyrites on their decomposition from 

 local causes, were replaced by that highly interesting 

 pulverulent mass reported so rich in gold. Now, I have 

 before me two letters from the Government Analyst, viz.: 

 one dated November, 1824, and the other October,' 1886, in 

 which the results of the analysis of "solid pyrites" from 

 that "Iron Blow" are given thus: — In the first letter 

 Mr. Ward states : " I have carefully tested the minerals 

 received .... have not been able to detect the 

 presence of tin or any other metal of commercial value;" 

 in the second he says : " In none of the samples forwarded 

 for assay have I been able to find more than traces of gold," 

 To these may be added those examples cited in Mr. Johnston's 

 paper, viz.: No. 9, "A sample of Iron Pyrites in which gold 

 is not mentioned as being present, and in No. 7 the sample 

 only shows "fine specks of gold just visible to the eye," but 

 this is not from pyrites, but from the soft purply pulverulent 

 mass, which is about 66 feet wide. 



On page 219, the author states: "Whether we suppose 

 that the ' Iron Blow' is due to hydro thermal agency or not, 

 there is nothing in the composition of the iron pyrites or the 

 dark purplish rock which necessitates their having been 

 originally formed in the way of volcanic mud." It is more 

 probable that the four principal elements, iron, barytes, 

 sulphur and gold, were originally precipitated from solution." 



Leaving out the references made in the paper in question 

 as to the production of gold elsewhere as foreign to the subject 

 under discussion, and which, however, are not altogether 

 accurate, I beg to direct your attention to the facts upon 

 which I join issue with Mr. Johnston's theory of origination. 



The analyses of Mr. Ward, cited by Mr. Johnston and 

 myself, conclusively prove the almost total absence of gold in 

 the pyrites, veins, or beds, which may be described as very 

 dense and excessively solid, and which undoubtedly have 

 resisted both decomposition and dissolution for ages ; how is 



