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CAPABILITIES WITH REFERENCE TO SETTLEMENT, 315 
surface increased, the effort would become more feeble. Around its bor- 
ders the forest is however still capable of spreading spontaneously where 
protection from fire is afforded; and it is observable, that in many direc- 
tions the prairie land has already reached its natural limit, and that its 
further extension, and the accompanying increase of drought, are checked 
against regions too much broken by irregularity of surface, or sub-divided 
by swamp and lake, to allow wide-spread conflagrations. 
_ 739. Many facts are already known which tend to show the progres- 
sive desiccation of the West in modern times; and explorers are con- 
stantly meeting with additional evidence of the same kind. Over the 
greater part of Montana, forest once destroyed is not naturally renewed, 
here and there a few trees are found which appear to be remnants of for- 
mer forests, and there is some reason to believe that ‘ even where undis- 
turbed by the hand of man, the forests are gradually disappearing from 
natural causes.”* Similar facts are also observed in California. In Da- 
kota, Prof. Thomas finds ‘dry lakes,’ or the dry basins where lakes 
formerly existed, now entirely devoid of water, and which do not appear 
to have been in this state many years. Even the lakes which still con- 
tain water, are said to have the appearance of decreasing year by year. 
There are also evidences of former swampy spots where the grass is still 
more luxuriant than that surrounding it, but the water has disappeared 
from the surface.”+ These hollows and lakelets no doubt resemble those 
of the second prairie plateau north of the Line, and though I believe 
many of the appearances bear other interpretations, there still appears to 
be a residuum of evidence in favour of change of climate for the worse. 
In south-western Minnesota, Prof. Winchell has recorded facts concerning 
the former deposit of calcareous tufa, which appear to have a similar 
bearing.{ Mr. Selwyn’s observations to the same effect on the second 
prairie steppe between the Qu’ Appelle and the Saskatchewan, have been 
already referred to, he writes with regard to the little lakes of the 
prairie :—‘“ They appear all to be gradually diminishing in size or drying 
up. This, Macdonald tells me, has been going on steadily for several 
years. He says that what were formerly large lakes are now small 
pools, and all the lesser ones are already quite dry, and their beds over- 
grown with grass and weeds.” § 
740. Evidence similar in teno1 to the above, is met with constantly 
*U.S. Geol. Surv. Territ., 1871. t+ U.S. Geol. Surv. Territ., 1872. p. 305. 
i *t Second§A nnual Report. Geoi. Surv., Minn., p. 197, 
$ Report of Progress. Geol. Sui v. Canada, 1873-74, p. 27. 
