[G. M. DAWSON] SECULAR CLIMATIC CIIANGi:S ' 163 



thtit since the year 1880, or possibly earlier, the water of many small 

 lakes and ponds without outlet, throughout the whole southern part of 

 British Columbia, has stood either permanently or for j)rolonged inter- 

 vals at levels higher than those attained (except possibly for very brief 

 periods) for forty, fifty or more years previous to that date. The period 

 of continuous low water in these lakes is thus cariied back from the 

 above date, continuously, to about 1830 or 1840 at the least. If the 

 evidence of Stumj:) Lake be accepted, it M^ould, however, tend to show 

 that a gradual increase in humidity had been in progress for at least 

 thirty years, of which the smaller lakes are found capable of registering 

 only the later stages, many of these having possibly been entirely dry in 

 earlier years. The observations show also a distinctl}' noticeable tendency 

 towards a decline in the general water-level at the present time. 



If it be supposed that the indicated change in climatic conditions 

 may be due to human agency, the partial removal of the naturally thick 

 grassy covering of open tracts of country, and the destruction of forests 

 by tire, are t]\e two most obvious possible causes. It may be suggested 

 that the first-mentioned circumstance might result in a freer drainage of 

 the bordering slopes toward the natural reservoirs, but in the cases of the 

 lakes referred to in the Eeport of 1885, and in that of those of the Green 

 Timber Plateau, the adjacent country has not yet been employed for past- 

 urage, or only to an insignificant extent, while the change in the condi- 

 tions of Stump Lake antidates the stocking of any part of the country 

 with cattle. Eespecting the destruction of forests, which has been con- 

 siderable, the only result which appears to have been proven to follow 

 such destruction elsewhere is that of decreasing the natural humidity of 

 the country, and it can therefore scarcely be called in to account here 

 for change in an opposite sense. Again, the permanent occupation of 

 any part of the inland portion of British Columbia did not begin before 

 1860, and the changes so far affected in any direction are verj' small 

 compared to the entire area of the country. 



It appears thus to be more than probable that the observed facts 

 point to some general climatic variation (Sjf a secular kind, rather than to 

 any change in conditions produced by man. It will be noted that all 

 the lakes and ponds referred to, lie within the area of the Cordillera 

 between the Eocky Mountains proper and the Coast Eanges, and that all 

 are situated in the naturally more arid portions of the southern part of 

 British Columbia. 



Numerous observations of change in level in lakes without outlet 

 have been made in late years in the southern part of the Cordilleran reo-ion 

 contained in the United States, but the most satisfactory and continuous 

 of these refer to the Great Salt Lake in Utah. In his monoo-raph on 

 Lake Bonneville ' Mr. G. K. Gilbert has collected and collated all the 



1 Monograph of the U. S. Geological Survey, vol. i., 1890. 



