ABRAHAM GESNER REVIEW OF HIS SCIENTIFIC WORK. 45- 



or hypogene rocks, and as he speaks of the associates of the 

 granite he also would include the gneisses and mica schists. He 

 now describes the clay slates and quartzites of the primary 

 district and those of part of his former " clay slate district " as 

 Cambrian — a natural out-growth of the improvement of geolo- 

 gical nomenclature, and parallel to his recent work in New 

 Brunswick. Under the head of Silurian Group he includes the 

 remainder of the " clay slate group " of his first book on Nova 

 Scotia. His fourth group is the " Old Red Sandstone," or 

 Devonian group, for the red rocks that were found below the 

 coal measures, etc. This is merged in the Lower Carboniferous 

 by later writers. The fifth division is the " Carboniferous rocks 

 or coal formation." The sixth is the " New Red Sandstone." 

 This division, extensive in the former work, is now limited to 

 certain strata near Ti'uro. The seventh group is the " Intrusive 

 and Igneous rocks " of the North Mountains. The eighth is the 

 Boulder or drift formation. This group was not recognized in 

 the earlier work, for in that the surface deposits are mentioned 

 casually in connection with the coherent rocks of the older 

 formations. Dr. Gesner attributes both the unstratified and 

 stratiged drift to the action of water, manifested through ocean 

 currents, floe ice, etc. 



Over thirty pages of this work are devoted to a description 

 of the economical minerals of Nova Scotia, with statistics of the 

 exportation of coal. 



Dr. Gesner lived in a period when the science of geology was 

 in its infancy. Hence we see proof, as we peruse his works, of 

 the gradual acquisition of new ideas upon the theoretical part of 

 the science. Now a geological surveyor enters upon his work 

 after a long course of preliminary training ; then he had to make 

 himself acquainted year by year with the rapid development and 

 new phases of thought in his favorite science. Now he enters 

 the field provided with the stores of knowledge accumulated in 

 the last one hundred years ; then he was slowly gathering those 

 facts and observing those phenomena which lie at the base of 

 geological theory. 



