THE FAST AND FUTURE OF GEOLOGY. 183 



matious were recognized, whereas now thirty-eight such are established, 

 and these are divided into about one hundred and twenty subdivisions, 

 each characterized by some peculiarity of structure or of fauna. Palaj- 

 ontology as a separate science was not then known ; structural and 

 physical geology had chiefly occupied attention ; but the study of or- 

 ganic remains has since advanced with such rapid and vigorous strides 

 that the older branch of the subject was until lately in danger of being 

 neglected and distanced. 



At that time, the number of species of organic remains in Great 

 Britain which had been described amounted only to 752, whereas now 

 the number amounts to the large total of 13,270 species. The relative 

 l)roportion between these totals and the numbers of each class is exhib- 

 ited in the annexed diagram, (Fig 1*,) which shows also the vast progress 

 made in palojontological knowledge between 1822 1 and 1874|. 



Some idea of the extent and variety of the past life of our globe 

 may be formed by comparing these figures with the numbers of plants 

 and animals now living in Great Britain. Excluding those classes and 

 families, such as the naked mollusca and others, which, Irom their soft 

 and gelatinous nature, decay rapidly and so escape fossilization, and 

 insects, || the preservation of which is exceptional, the number of living 

 species amounts to 3,989, against 13,183 extinct species of the same 

 classes, and the relative proportions of each class stands as in the dia- 

 gram. Fig. 2. 



Thus while the total number of those classes of vertebrate and inver- 

 tebrate animals and i^lants represented in a fossil state, and now living 

 in Great Britain, is only 3,989, there formerly lived in the same area as 

 many as 13,27G species, so that the fossil exceed the recent by 9,287 

 species. It must be remembered also that plants are badly represented; 

 for owing to their restricted preservation, the fossil species only number 



* lu these diagrams, the iuuer semicircle, a a, gives the relative proportiou between 

 each class in an area which represents the sum of the total ; and the outer semicircle, 

 c c, gives the dimensions which each class would have had had the pi'oportions between 

 the several classes in each of the two compared periods or stocks been maintaiued in 

 the same ratio as in a a ; while the irregular segments bh give approximately the actual 

 increase or excess of each class, showing how comparatively large the additions in some 

 of them have been compared with those in others, aud in the case of Fig. 2 showing how 

 particular classes of fossils fall below or exceed in development of their living ana- 

 logues. The inner numbers attached to the several classes refer to the value of each 

 in the inner circle a a, and the outer numbers have reference to the values represented 

 by the segments 6. The sign X means that certain segments should be so many times 

 larger. 



t As there was no list of British fossils then published, I have taken the numbers 

 given in Woodward's " Synoptical Table," published in 1830, and deducted from them 

 those added to the stock betwcsen 1822 and 18.30. 



1 1 am indebted to my friend Mr. Etheridge, F. 11. S., paheontologist to the Geological 

 Survey, for the particulars of this 1874 stock. The details are given in a valuable 

 table, which he has had the kindness to draw up for me, and which is given in full, 

 with the details of the 1822 stock and of living species, in the ai)pendix. 



II The number of British species of insects amounts to between 10,0U0 aud 11,000. 



