1895-96.] RAINFALL AND LAKE LEVELS. 125 



The two principal factors governing the level of the water in any one of 

 the various lakes are the precipitation over its own drainage area and the 

 stage of the water in the lake above it. Other factors are evaporation, 

 wind, etc.: but these we must at present regard as fairly constant, as a 

 consideration of them would. entail an immense amount of work. I had 

 thought before charting the curves for Lake Superior that the mean 

 rainfall as deduced from the observations at the three stations before 

 named would give a very fair approximation to the precipitation over the 

 water-shed of that lake, and Lake Superior being the head of the chain, 

 and the rivers and streams emptying into it being for the most part 

 small, I should at once find a very clear and undoubted similarity be- 

 tween the annual lake level and rainfall curves, but I was disappointed. 

 The mean annual level does not seem to respond in by any means a 

 satisfactory manner to the changes in the mean annual rainfall, as deduced 

 from the three stations before named ; and the most probable explana- 

 tion of the discordance is that the rainfall curve is not based on sufficient 

 data, and does not shew the true state of affairs. The greater part of 

 the drainage area of Lake Superior lies to the north, a region where 

 until but a few years ago no observations of the rainfall were taken 

 For eight years, however, a regular record has been kept at White River, 

 at which station during 1893-4-5 the rainfall was much in excess of the 

 average of the eight years, and would form a curve well in accord with 

 the lake levels, whereas the rainfall over the western portion of the lake 

 was below average. It is then obvious that we are not at present in a 

 position to draw a curve shewing with a sufficient degree of accuracy the 

 rainfall over the water-shed of Lake Superior. 



We will now briefly consider the state of affairs in the region of the 

 great lakes since 1870, assuming as a fact that the level of that lake is alto- 

 gether governed by rainfall over its own drainage area. In 1870 the levels 

 of Superior and Huron were medium, but during the autumn an abnormal 

 fall of the former began. The summer stage of Ontario in this year was 

 very high, clearly owing to one of the largest rainfalls on record occurring 

 over its drainage area. The two following years were low water years on 

 Lake Superior, and Lake Huron felt the effect of it, and with a rainfall of 

 3.1 inches below average in 1871, and 4^0 below in 1872, the water level 

 was in the latter year fairly low. The diminished head of water in the 

 higher lakes, and a precipitation several inches less than average, brought 

 a rapid lowering of Ontario, and 1872 was a year of decidedly low water. 

 During 1873 Lake Superior was a trifle above mean level, and this fairly 

 good level seems to have outweighed an under average ramfall in the Lake 

 Huron area, as that lake although still low was slowly rising. Ontario 

 rose very considerably in this year, notwithstanding the low water in the 



