OPHITES,, SEDIMENTARY AND IGNEOUS. 45 



CHAPTEE IX, 



MANY OPHITES WERE SEDIMENTS, AND OTHERS 

 IGNEOUS ROCKS ORIGINALLY, 



UNTIL the discovery of stratified ophites in the Laurentian 

 series of Canada, few geologists thought otherwise than that the 

 rocks under consideration were of igneous origin. Most of the 

 ophites known on the Continent favoured this view ; and, not- 

 withstanding their mineral and plainly bedded characters, the 

 ophi-calcites of Conneinara, it was conceived, were no more 

 sedimentary than the whin-sills of the north of England and 

 other stratified dolerites. 



The discovery that the Canadian ophites were the products 

 of sedimentation, it may well be imagined, greatly perturbed 

 the opinion which had prevailed previously. 



It next behoves us to mention that for many years before 

 Canada had been geologically surveyed, mineralogists, through 

 the researches of Blum and others, had become acquainted with 

 the fact that serpentine, the essential mineral of the rocks in 

 question, is a product of the chemical alteration of other 

 minerals. Still few geologists seemed to appreciate in full the 

 bearing of this fact upon rock-masses of serpentine. 



Again, the discovery of the presumed organic structures in 

 the Canadian ophites by Logan, Dawson, and Carpenter, was 

 generally admitted to be a fatal blow to both the igneous and 

 the chemical-alteration theories. 



The evidences educed by our investigations connected with 

 the last-mentioned discovery, however, have unexpectedly led to 

 conclusions totally different from those which originated in the 

 Canadian school of geologists. What has already been stated 

 makes it quite unnecessary to dwell further on this point : suf- 

 fice it to say, that the conclusion we have adopted as to the 

 origin of ophites is the same as the one foreshadowed by the re- 

 sults which attended the labours of Blum and others on mineral 

 pseudomorphism . 



Having already noticed in detail the ophites of sedimentary 



