138 Barrell — Growth of Knoivledge of Earth Structure. 



have been correct in all essential .particulars, were for a 

 generation submerged under the propaganda carried for- 

 ward by the disciples of Werner. The ' i Illustrations of 

 the Huttonian Theory of the Earth," a remarkable clas- 

 sic, worthy of being studied to-day as well as a century 

 ago, was published in 1802 by John Playfair, professor of 

 mathematics in the University of Edinburgh and a friend 

 of Hutton, who had died live years previously. This 

 volume was opposed by Robert Jameson, professor of nat- 

 ural philosophy in the same university, who had absorbed 

 the ideas of the German school while at Freiberg 

 and published in 1808 a volume on the "Elements of 

 Geognosy," in which the philosophy of Werner is fol- 

 lowed throughout and even obsidian and pumice are 

 argued to be aqueous precipitates. The authority of the 

 Wernerian autocracy caused its nomenclature to be 

 adopted in the new world, but strong evidence against 

 its interpretations was to be found in the actual struc- 

 tural relations displayed by the igneous rocks. 



Contributions on Volcanic and Intrusive Bocks. 



The accumulation and study of facts constituted the 

 best cure for an erroneous theory. The publications of 

 the Journal contributed toward this end by articles along 

 several lines, the most original contributions were those 

 which dealt with the areal and structural geology of 

 eastern North America, but equally valuable at that 

 time for the broadening of scientific interest were 

 the studies on the volcanic activities of the Hawaiian 

 Islands, published through many years. Perhaps most 

 valuable from the educative standpoint were the exten- 

 sive republications in the Journal of the more important 

 European researches, making them accessible to Ameri- 

 can readers. In volume 13 (1828), for example, a digest 

 of Scrope's work on volcanoes is given, covering forty 

 pages ; and of Daubeny on active and extinct volcanoes, 

 running over seventy-five pages and extending into vol. 

 14. Through these comprehensive studies the nature of 

 volcanic action became generally understood during the 

 first half of the nineteenth century and the original pub- 

 lications in the Journal were valuable in giving a knowl- 

 edge of the activities of the Hawaiian volcanoes. 



Early in the nineteenth century the whole of America 

 still remained to be explored by the geologist. The 



