94' Correspondence — Mr, David Forbes. 



from those already in office or authority, who are sure to be jealous of intruders on 

 what they imagine to be their own domain, and, doubtless, dislike having their 

 peace of mind disturbed by innovations. 



A discussion of this nature may be carried on in two ways, either by considering 

 the main points of the argument first, before engaging in the minor details, or the 

 reverse ; Dr. Hunt prefers the latter course, which, no doubt, is best suited to the 

 defence of a weak cause, but which his rather rambling remarks in last week's 

 Chemical News^ will show is not calculated to convey to his reader any very clear 

 idea of the exact points at issue, and is likely to confuse by then umber of minor 

 details, having little or no bearing upon the main questions. 



It is, therefore, most important for me that no misunderstanding should arise as 

 to the exact points on which I have presumed to differ from the principles of 

 chemical geology which Dr. Hunt has recently brought before the scientific public 

 in Europe. 



Expressed in as few words as possible, I object to the following of Dr. Hunt's 

 assumptions or assertions : — 



1. That the earth is solid to the core. 



2. That the surface of the earth, immediately previous to its entire solidifica- 



tion, was "a liquid bath of no great depth surrounding the solid nucleus," 



3. That the original atmosphere contained " the whole of the chlorine in the 



form of hydrochloric acid, the sulphur as sulphurous acid. " 



4. That the saltness of the sea is due to a rain of hydrochloric acid ''flooding 



the half-cooled crust" with a highly heated acid deluge. 



5. That the whole of " the calcareous strata, the marbles, and various limestones 



which we find on the earth's surface" have been precipitated from the sea 

 by carbonate of soda. 



6. That all the magnesian limestones and gypseous beds were formed in a dense 



atmosphere of carbonic acid. 



7. That quartz "can only be generated by aqueous agencies." 



8. " That granite is in every case a rock of sedimentary origin." 



9. That volcanic rocks are merely ordinary sedimentary beds, melted by being 



"depressed, so that they come within the action of the earth's central 

 heat." 



Any minor differences fall naturally under these heads, and I may add that the 

 perusal of Dr. Hunt's defence has confirmed me more than ever in the belief that 

 the above premises are unsound, and I shall now endeavour, as concisely as possible, 

 to examine the arguments pro et contra. 



I. — The earth solid to the core. 



Dr. Hunt seems to imagine that if the earth is not solid to the core, it can only 

 consist of an immense central sphere of molten matter covered by a thin external 

 crust or shell, for he wastes all his arguments in attempting to upset this theory, to 

 which I had never given my adhesion. 



I have preferred adopting in the main the hypothesis of Bunsen, no mean 

 authority, and when opposing Dr. Hunt's views simply asserted my opinion that 

 the earth still encloses "a vast reservoir or reservoirs of still fluid igneous matter 

 in its interior ;" and the main argument with winch I support this opinion is, that 

 I consider that the molten lava ejected from volcanos must be derived from some 

 such source. This is a veiy simple but common-sense view of the case, which I 

 imagine Dr. Hunt will find some difficulty in refuting. 



II. — That the earth's surface immediately previous to its entire solidification was 

 "a liquid bath of no great depth surrounding the solid nucleus." 



Hopkins has taken into favourable consideration the supposition that the earth 

 actually was solid both in its centre and crust, and yet might retain fluid igneous 

 matter in the intermediate space ; and taking a somewhat similar view of the case, 

 I believe that, even allowing that the solidification actually did commence at the 



1 It is necessary to explain here that many of Dr. Hunt's observations refer to a previous 

 communication in the October Number of the Geological Magazine, and not to the subsequent 

 one in the Chemical News of Oct. 4, which, as is distinctly stated therein, i.«, only supplementary 

 to the former and to be read in conjunction with the same ; yet Dr. Hunt indulges in the absurd 

 accusation, that the contents of that communication have, "for some unknown reason, been 

 withheld from the readers of the Chemical News" 



