226 ROCHESTER ACADEMY OF SCIENCE. [APRIL I4, 



to the coming of severity from directly north or northwest. A more 

 correct statement would, perhaps, be that it stands a complete 

 barrier to the utmost severity being felt here, for the cold may pass 

 overhead and strike further south. This is so, and must be so, 

 because so long as the water is unfrozen the air in contact with it 

 must take the temperature of the water, which cannot be much below 

 32 degrees, and this will heat up the lower layer which is felt here 

 while the great cold may be passing over higher up. In such a move- 

 ment the surface air must necessarily be from north to south, which 

 brings the air of the lake surface directly on us. 



PRECIPIT.\TION. 



As to precipitation, it may be said in a general way that, as with 

 the temperatures, moderation prevails here. This place is not dis- 

 tinguished with high or low annual, monthly, seasonal or daily 

 precipitation. The only place it reaches high rank in this connection 

 is in the number of days rain or snow falls. Here it comes near the 

 ape.x of experience in the United States. It takes somewhat high 

 rank in the even distribution of precipitation through the months and 

 seasons. No complete comparison of the departures from year to 

 year can be given, but it is less here than most places. The average 

 annual rainfall is about 34 inches against an average of 36 inches for 

 the entire country. A sufficiently close comparison of seasonal with 

 the average of the whole country is given elsewhere. The frequency 

 of days with one-hundredth of an inch or more is supposed to be 

 somewhat greater at Oswego than here ; outside of that one place 

 Rochester holds the banner position. This frequency comes, however, 

 largely from the fall of unimportant light lake snows during the winter. 



The probability of rainy days ranges from 65 out of the hundred 

 in January to 32 in August, against 41 in January to 33 in September 

 at Boston and San Francisco ; 65 in January to 13 in August at Port- 

 land, Ore, In evenness our record is superb in both number of days 

 and amounts per month and season. In normal for months the 

 record here is from 3.34 inches in May to 2.44 in .September, against 

 4,60 in November to 3 in September at Boston ; 4.80 in August to 3 

 in .May at New York ; 3.80 in October to 2.40 in April at Buffalo ; 

 3.70 in July to 2.20 in December at Chicago ; 5.70 in July to 0.70 in 

 February at Omaha ; 4.00 in P'ebruary to trace in July at Los Angeles ; 

 5.30 in December to trace in July and August at .San Francisco ; 8.00 

 in December to 0.60 in July and August at Portland ; 3.70 in July to 

 0.60 in January, February and November at St. Vincent ; 14.40 in 



