256 ROCHESTER ACADEMY OF SCIENCE 



to his death, May 1, 1918, he was continuously on the national 

 survey. 



Gilbert was not a prolific writer, as compared with others and 

 judged by his work and abihty. Down to 1891 the bibliographic 

 Hst carries 70 titles, four of which have associated authors. His 

 initial publication, in recognized geologic mediums, was in 1871, 

 on the Cohoes Mastodon in the twenty-first annual report of the 

 New York State Cabinet of Natural History. His next three 

 articles have been noted above, relating to Ohio geology and the 

 ancient beaches. From 1871 his papers are mostly in description 

 of features of the western country. The most important of his 

 earlier papers is the report on the Henry Mountains, published 

 1877. In this classic paper he described a new type of mountains, 

 now fully recognized. These were originally domes, or areas of 

 sedimentary strata lifted by the injection of lava from beneath. 

 Quoting his own description, page 19: 



"The lava of the Henry IMountains behaved differently. Instead of rising 

 through all the beds of the earth's crust, it stopped at a lower horizon, 

 insinuated itself between two strata, and opened for itself a chamber by 

 lifting all the superior beds. In this chamber it congealed, forming a mas- 

 sive body of trap. For this body the name laccolite (cistern-stone) will be 

 used." 



In later years the name has been changed to laccolith. Subse- 

 quent erosion of these uplifts by doming has often destroyed the 

 arching form or obscured the primitive shape and exposed the 

 injected igneous heart. The latter part of this book is a discussion 

 of land sculpture. In this statement of the principles of erosion and 

 the origin of topographic forms he shares with Newberry and 

 Powell the honor of a pioneer. 



Probably his most famous writing is the work on Lake Bonne- 

 ville. This is the initial volume of the series of quarto monographs 

 published by the National Survey, and bears the date 1890. This 

 describes the wide expanded predecessor of the present Great Salt 

 Lake, which existed in glacial time when humidity and rainfall of 

 the Great Basin produced the vast lake which overflowed north- 

 ward to the Columbia River. Great Salt Lake is only the saline 

 remnant of that dessicated fresh-water body. 



