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memoirs published by the officers of the Survey, to the beautifully 

 illustrated ' Decades,' in which Prof. Forbes's artistic skill and judg- 

 ment are so manifest; his Monograph on the British Naked-eyed 

 Medusae, published by the Ray Society ; and the large work on the 

 ' Natural History of the British Mollusca,' undertaken and finished 

 in conjunction with Mr. Hanley are sufficient evidence that his 

 active mind was not one of those which are oppressed and over- 

 powered by details. 



Among these many contributions to science there are two so 

 marked by originality and genius, so pregnant with results for the 

 future, as to deserve more than passing notice. The first of these is 

 the ' Essay on the Distribution of the Fauna and Flora of the British 

 Isles,' in the first volume of the Memoirs of the Survey, which may be 

 characterized as one of the happiest applications of the facts of one 

 science to the elucidation of the difficulties of another that has ever 

 been made. The doctrine laid down in this memoir is, that the 

 existing distribution of animals and plants can only be regarded, 

 not as a primary and independent phenomenon, but as the result of 

 previously existing conditions, as the product, in fact, of two fac- 

 tors ; the one, the successive changes of living beings in time ; the 

 other, the successive changes of the position and boundaries of land 

 and sea in space. 



The second work here adverted to is that remarkable Essay on 

 the Tertiary Beds of the Isle of Wight, the fruit of Prof. Forbes's 

 last labours. 



By an elaborate study of the Purbeck beds in Dorsetshire in 1850, 

 Prof. Forbes had come to the unexpected conclusion that they were 

 divisible into three formations, each characterized by distinct sets of 

 fossil remains ; and that the freshwater mollusca and foraminifera 

 of the Purbeck beds, to which he had given his more particular 

 attention, did not agree specifically with the fossils of the incumbent 

 Hastings Sands. The latter he proposed to class as Lower Creta- 

 ceous or Neocomian, while the Purbeck he henceforth considered 

 as an uppermost member of the Oolitic group. His great success 

 in these researches awakened in him a lively curiosity to examine 

 in like minute detail the great series of tertiary freshwater strata 

 occurring in the northern part of the Isle of Wight. Accordingly, 

 he devoted several months in the autumn and winter of 1852 to the 



