T 



V. 



Life- Zones in Lower Palaeozoic Rocks. 



HE " Records of the Rocks," which had been assiduously 



-I- collected for some time past, were first arranged in definite 

 order by William Smith during the close of the last century and the 

 commencement of the present one. It is well known that Smith's 

 work gave an impetus to the study of Stratigraphical Geology, which 

 resulted in the establishment of a chronological sequence of strata in 

 many areas during the early decades of this century. It is a tribute 

 to the acumen of British geologists that many of the terms which 

 they adopted for the major subdivisions of the strata are now in 

 general use in all parts of the world. But the work of correlation, so 

 enthusiastically commenced, received a check. Dr. Whewell and 

 Mr. Herbert Spencer questioned the possibility of assigning the same 

 age to similar deposits in remote areas, and the difficulties of the 

 task were forcibly presented to geologists by Professor Huxley in his 

 Presidential Address to the Geological Society in 1862. Some time 

 previously to this, M. Barrande (i) had called attention to the ap- 

 parently anomalous distribution of organisms in the rocks of the Lower 

 Palaeozoic Basin of Bohemia, on which was founded his well-known 

 doctrine of " Colonies," and in later publications he instanced a large 

 number of re-appearances of organisms in the rocks of the same 

 basin, which he cited in support of his doctrine. Correlation of strata 

 was, after this, looked upon with considerable suspicion. Nor is this 

 to be regretted, for one result was the diversion of the energies of 

 many most able workers into another field, that of petrological 

 research, which has of late years yielded so many brilliant results. 



The then comparatively little known Lower Palaeozoic Rocks 

 were, perhaps, the special objects of distrust at the time of which I 

 have been speaking, for it was in these rocks that the colonies were 

 asserted to exist, and subsequent research brought to light a number 

 of other cases of which the once-accepted explanation was strongly 

 adverse to successful correlation. The theory of colonies has now but 

 few supporters, and many of the other apparent cases of anomalous 

 vertical distribution of organisms have been proved to be due to 

 errors of interpretation. 



A new era in the study of rocks of greatly disturbed districts was 

 inaugurated l)y the publication, in 1878, of Professor Lapworth's 

 remarkable paper on " The Moffat Series," (2) in which the method 



