t^8 Rev. 0. Fisher — Contraction of Roclis in Cooling. 



III. CONTBAOTION OF EOCKS IN CoOLING. EePLT TO D. FoKBES, 



Esq., F.E.S. 

 By Eev. 0. Fishee, M.A., F.G.S. 



IN replying to Mr. Forbes' strictures upon my paper at Cambridge 

 upon "The elevation of Mountains, etc," I may be permitted 

 to say, what would otherwise be of no consequence. The paper was 

 read in April 1868. I received it back from the referees, accom- 

 panied by some valuable suggestions, in September. I was at that 

 time much occupied, and did not work out those suggestions until 

 January 1869. After having done so I wrote to Mr. Forbes, re- 

 ceived his reply on the 29th, and a week later sent the paper back 

 to the referees. 



Although, therefore, as Mr. Forbes infers, the paper was altered 

 subsequently to its being read, yet those alterations were not made 

 without the sanction of the officials of the Society. 



It seems to me that the more rocks contract in cooling, the more 

 probable it is that the earth is solid. And I conceive that this must 

 be a question of degree, unless we consider melted rock to be a 

 perfect fluid. 



I understood the same view to pervade Mr. Forbes's paper " On 

 some points in Chemical Geology." Hence in quoting from his 

 paper, in which he inclines to support the opinion of the earth's 

 fluidity, I felt that I was not using data furnished by an advocate 

 of the side of the question favourable to my theory ; for that was 

 based on the contraction of the earth in cooling. It was this, and 

 nothing more, which prompted the expression, that Mr. Forbes was 

 " concerned to reduce, as much as possible, the contraction of the 

 materials of the earth." If the words he capable of a sinister mean- 

 ing, I should have been ashamed to have used them in it. 



The reply which I received from Mr. Forbes to my inquiry, 

 whether he had allowed for the expansion of the iron moulds, was as 

 follows : — " The expansion of the moulds was allowed for in many 

 cases by measuring the liot moulds, which was easily done, since the 

 moulds were in all cases cubes or rectangular. Other experiments 

 were made both in stone and sand moulds. The results obtained by 

 me are not put forward as representing the true amount of contrac- 

 tion, but as showing," in short, that Bischoff's results were consider- 

 ably too large. 



I did not alter what I had written because the qualifying words, 

 "in many cases," led me to think (wrongly it appears), though hot 

 moulds were in many cases used, yet that the dimensions given in the 

 Chemical News were probably those of the moulds when cold.^ This 

 idea was confirmed by the disclaimer of exactness for the results. I am 



^ "The slags were allowed to flow into iron moulds, ten inches long by six deep 

 and wide, also containing 360 cubic inches, a heavy iron top-plate being dropped 

 upon them when overflowing, so as to ensure theii" being filled completely and 

 evenly." — Chemical News, vol. xviii., p. 193. 



