Eminent Living Geologists : Rev. Osmond Fisher. 51 



Mr. Fisher's removal to Harlton was almost concurrent with 

 3, change in the nature of his work. Pure geology was not, indeed, 

 neglected, but it gradually gave place to the study of the great 

 problems presented for solution by the earth's crust. The British 

 Association met at Norwich in 1868, and Mr. Fisher was invited to 

 open the proceedings of the Geological Section with a paper on the 

 " Denudations of Norfolk." The coprolite deposits of the Cambridge 

 •Greensand and the mammaliferous deposits at Barrington also occu- 

 pied a good deal of his attention, and form the subjects of papers 

 read before the Geological Society in 1872 and 1879. 



It is interesting to notice that Mr. Fisher, who is now the foremost 

 opponent of the contraction theory, was many years ago one of its 

 strongest advocates. He was, indeed, an independent discoverer of 

 the theor}'. It occurred to him as early as 1841, the year in which 

 he took his degree, and was suggested by the ridging up of cracked 

 and re-frozen ice in one of the locks of the river Cam, In his delight 

 at the discovery, he tells us. he forthwith vaulted over a five-baned 

 gate. The idea, however, lay apparently dormant for many years ; 

 and it was not until April, 1868, that the first of his three well- 

 known memoirs was read before the Cambridge Philosophical 

 Society. At this time Mr. Fisher was orthodox in his views. He 

 accepted the solidity of the earth's interior on the authority of Lord 

 Kelvin as " almost certain," and considered that the outer crust 

 would lose the support of the inner portions " probably from the 

 effects of contraction in cooling." 



"When he is presented with a new theory, Mr. Fisher's first 

 impulse is to test it numerically. The cause invoked may be a true 

 one, but is it also sufficient ? Is it capable of producing effects of 

 the amount as well as of the kind observed ? Here the mathe- 

 matician steps in with advantage and offers useful aid to the 

 geologist. In Mr. Fisher's first memoir the process is applied to 

 the contraction theory. He shows that, if an outer spherical shell 

 could be isolated from the mass within, it would at once be crushed 

 by lateral pressure till it rested on that mass. The contraction 

 theory thus invokes a true cause of rock-folding. To prove the 

 sufficiency of the theory, he calculates roughly the order of magni- 

 tude which mountain-ranges, if so formed, might be expected to 

 assume ; and concludes that " the theory seems to be at any rate not 

 deficient in its capability for producing the results attributed to it." 



Five years later, in June, 1873, we find Mr. Fisher defending the 

 contraction theory against Captain F. W. Hutton in the pages of this 

 Magazine ; but, within a very few months, his allegiance to the 

 theory must have begun to waver. The paper referred to contains 

 the groundwork of his estimate of the mean height of the surface- 

 elevations of the globe. He was then led to calculate more closely 

 the mean height of the elevations that would be produced by the 

 contraction of the earth in cooling ; and his work is described in 

 a second memoir read before the Cambridge Philosophical Society in 

 December, 1873. The discrepancy is so great (more than 9000 feet 

 in the one case, and less than 800 feet in the other) that Mr. Fisher 



