Reports and Proceedings — Geological Society of London. 187 



He then dealt with the recent evidence bearing on the Geoh^gical 

 and Biological History of early Cambrian and Pre-Cambrian Times, 

 pointing out that very different views are now held in regard to 

 the origin of many of the Pre-Cambrian rocks from those which 

 prevailed from twenty to thirty years ago. Then all the crystalline 

 schists and gneisses, and many also of the granitic rocks, were 

 looked upon as metamorphosed sediments. Gradually, and mainly 

 from the careful microscopical work which has been carried on by so 

 many eminent petrologists in this and other countries, we have been 

 led to recognize that a very large proportion of the crystalline 

 rocks previously supposed to have been sediments are igneous 

 rocks which have been crushed, cleaved, and have suffered other 

 changes from chemical and mechanical influences. It has been 

 shown also that very large and unexpected proportions of the Pre- 

 Carabrian rocks were built up from materials derived from volcanic 

 outbursts, and that this was particularly the case in the British 

 areas. As a consequence, few of the sediments are such as could 

 have been deposited in marine areas favourable to organic life, or 

 are such as would be likely to retain very definite evidence of its 

 existence: Still, the very earliest of the Cambrian rocks, or those 

 sediments which were deposited in a fairly tranquil sea, following 

 the great physical changes which took place at the close of the 

 Pre-Cambrian era, contain ample evidence that the sea which was 

 gradually encroaching on the Pre-Cambrian land on both sides of 

 the Atlantic teemed with life, in which probably all the orders of 

 the Invertebrata were represented. 



These discoveries had undoubtedly added most important evidence 

 in support of the theory of the gradual evolution of organic life, 

 and led one to speak very hopefully of finding yet earlier traces of 

 the life-history of our globe. The readiness with which suitable 

 forms tenanted all the areas as they were covered by the sea showed 

 that there was abundance of life near at hand in the adjoining 

 submerged areas, and that the changes then taking place were 

 only such as had been going on more or less continuously on the 

 surface of the globe from the moment when the waters began 

 to collect or, at any rate, became suitable for the existence of 

 life. The earliest records may have been completely blotted out by 

 the repeated changes which had previously taken place, or may 

 be entirely buried beneath and hidden from our view in the great 

 oceanic areas. Still, the results obtained within comparatively 

 recent years led one to hope that there is yet room to discover much 

 in those areas which hitherto have been but imperfectly examined 

 or not at all explored. 



The President concluded that as geologists we feel quite certain 

 that from the earliest Cambrian to tlie present time we are dealing 

 only with a comparatively recent period in the world's history ; 

 and, as biologists, that we are convinced that innumerable succes- 

 sions of organic beings must have lived and passed away in the 

 Pre-Cambrian era before such an advance could have been attained, 

 as is manifest in those forms which tenanted the earliest Cambrian 



