272 



ON THE HYDROLOGY OF THE BASIN 



arable prairie, along the streams through which, where there is a local supply of moisture, 

 wood is found, but yet the whole lias much less moisture than the naturally woody por- 

 tions. The uncolored, or white portions of the map, within the boundary of the United 

 States, indicate the regions so deficient in moisture, that no dependence can be placed 

 upon them in regard to agriculture. In some parts of them, where moisture is found, 

 crops may be produced ; but as a whole they are of little value in the way of affording 

 the necessaries of human existence, and are incapable of maintaining more than a very 

 sparse population. 



For so much of this map relating to the United States, and as an authority for the; 

 statements now made, the author is indebted to Dr. Henry. 



The author has added to this statement the result of four years' observations upon the 

 rain-bearing winds in Canada (Appendix, No. 9), by which it appears that out of the 

 whole quantity of rain which fell at Montreal, during the years 1858, 1859, 1860, and 

 1861, the following proportions were derived from the west, northwest, and north, namely: 

 1858, 28 per cent. ; 1859, 36 per cent. ; 1860, 28 per cent. ; 1861, 30 per cent. ; giving 

 an average for the four years of 30 J per cent., while from the other points of the compass 

 during the same period, the average was 67 i per cent.; showing immediately the direc- 

 tion and tendency of the rain-bearing winds, which, while their duration is limited to 

 only a very few days in the year, furnish about three-fourths of all the rain and snow 

 precipitated. 



The result of a series of observations on the daily maxima and minima ranges of tem- 

 perature is appended hereto (Appendix, No. 9), and the diagrams for the years which have 

 been mentioned are given in full, showing results confirming what must have struck the 

 most general observer of the weather in the Valley of the St. Lawrence, viz., the most re- 

 markable and sudden fluctuations in temperature, and in the proportion of cloud. 



The two features have been projected upon the same paper, and will be studied with 

 interest, if not on account of the particular feature mentioned, yet in regard to the more 

 salient features of actual temperature and its extreme fluctuations. (Plates IV, V.) 



Observations have been established at several points in Canada ; but before arriving at 

 any generalizations, observations would require to be continued for a much longer period. 

 It has, however, been observed in Canada, as in those parts of New York lying contiguous, 

 that the temperature of the months increased from the first half of February to the last 

 half of July, from which it regularly returns to its minimum in February, as shown in a 

 diagram before referred to. The mean of the second half of April, and of October, in the 

 general group of observations, differs but little from the annual mean. 



Lakes or large bodies of water are found to exert an equalizing influence on the tem- 



