ABSTRACTS OF PAPERS READ JANUARY 2 557 



the mountains of central Idaho, the cold timberline is sharply drawn at an eleva- 

 tion of about 10,000 feet, while the dry tin:ber]ine, equally well defined, has an 

 elevation of about 7,000 feet; between the two there is a belt of forest trees which 

 encircles the mountains. In southeastern Oregon, Nevada, southern California, 

 etcetera, where the climate is excessively arid, the dry timber-line is higher than 

 in Idaho, and in certain localities meets the cold timberline, and the mountains are 

 bare of trees from base to summit. The dry timberline decreases in elevation 

 when traced from arid to humid regions. In the central part of the continental 

 basin of North America it defines the border of the treeless portion of the Great 

 plateaus and the prairie plains, and at the north coincides with the southern limit 

 of the sub-arctic forest. On the borders of the treeless plateaus and the prairie 

 plains the position of the margin of the encircling forest is determined mainly by 

 lack of moisture, but is varied locally by soil conditions, hot winds, forest fires, 

 etcetera, in the same manner that the lower limit of tree growth on the mountains 

 of arid region is regulated. 



When the humidity is sufficient for the growth of trees, as, for example, on the 

 mountains of New England, the dry timberline disappears. An arid region may 

 be bordered at a lower elevation by a region with sufficient humidity to permit 

 trees to grow, and may then be bordered both above and below^ by the dry timber- 

 line, as is the case in southern Idaho. Where an arid region reaches sealevel, 

 as in Arizona, southern California, and the west coast of Mexico, etcetera, there 

 is no forest below the arid belt, and in certain localities the dry timberline meets 

 the cold timberline, and the mountains are bare of trees from sealevel to their 

 summits. 



There is also a third general cause which draws a limit to timber growth, namely, 

 excessive humidity, as, for example, on the borders of swamps, the margins of 

 lakes, etcetera, which may perhaps be termed the " wet timberline." 



WORK OF THE GEOLOGICAL SURVEY OF CANADA IN 1902 

 BY EOBEKT BELL 



\_ Abstract] 



The different classes of workers, their numbers : Field work ; the parties which 

 were sent out, objects to be attained, means employed; regions surveyed and ex- 

 plored from the Yukon district to Nova Scotia ; some of the results. Work relating 

 to mines and economic geology ; to chemistry, mineralogy, and petrography ; the 

 publication of serial reports and special treatises with illustrations; artists' work; 

 labors of the staff" in paleontology, zoology, economic botany, fruit growing. The 

 extension of agriculture in the north, forestry, forest fires, preservation of timber ; 

 necessity for topographical surveying in unexplored regions; the compilation and 

 engraving of maps, those published and those in course of preparation during the 

 year; making of illustrative models of sections and surface relief; work in connec- 

 tion with the museum and library ; aid given to education, distribution of reports, 

 maps, suits of named specimens of minerals and rocks; the collecting of fossils, 

 rocks, and minerals ; the preparation of pamphlets and descriptive catalogues 

 showing the mineral wealth of Canada; displays of economic minerals, etcetera, 

 at international exhibitions; contributions to archeology and ethnology; exten- 

 sive correspondence of the department, great variety of subjects treated of; infor- 



