70 TWENTIETH ANNUAL REPORT ON THE STATE CABINET. 



and ten, would be very nearly the temperature of the warmest 

 and the coldest seasons in the northern hemisphere, if the earth 

 were a globe uniform in its surface and none of the causes, which 

 I have enumerated above and proceed to consider below, were at 

 work in causing variations. 



It will be observed, also, in the above Table, column fourth, 

 that the hottest day at the equator is March 20th (the same is 

 true also of Sept. 22d), and at lat. 5 the hottest day is April 2d ; 

 and the farther north the later, until we reach the Tropic of 

 Cancer and June 21st. But in fact the greatest heat is not reached 

 until some days after that which is thus indicated as the hottest. 

 Within the tropics this difierence is slight, perhaps nothing ; but^ 

 as we pass towards the pole, it becomes perceptible. In our lati- 

 tude the heat does not reach its maximum, as appears on an ave- 

 rage of fifteen years, until the first day of August, or about six 

 weeks after the summer solstice. This is owing to the fact that 

 wdiile the sun is decreasing in altitude and the days are decreasing 

 in length, the earth is receiving more heat during the day than 

 it radiates during the night, and it is thus accumidating and hoard- 

 ing up heat, if we may use such an expression. 



Hence, for this and other reasons, to be discussed below, we 

 have in all high latitudes days that are colder, and days that are 

 much warmer, than the extremes above indicated. Within the 

 tropics, however, and near them, it is not likely that a degree of 

 cold so great as is indicated in the Table is ever anywhere expe- 

 rienced at the level of the sea coast. 



II. The next cause influencing climate, in the order of our enu- 

 meration is, elevation above the sea level. 



It is commonly held, that as we ascend from the sea level, the 

 air grows colder at the rate of about one degree for every three 

 hundred feet of ascent. This is owing to the fact that the air 

 receives but very little warmth from the direct rays of the sun as 

 they pass through it ; consequently, the air depends for its tempe- 

 rature chiefly upon the heat that it receives both by radiation and 

 conduction from the earth. That the temperature grows colder as 

 we ascend, all persons know ; and even under the equator, snow 

 becomes perpetual at an elevation of about sixteen thousand feet. 



By referring to the preceding Table, it will be seen that between 

 latitudes 35 and 60, an elevation of about 300 feet, diminishing 

 the average temperature one degree according to the above rule, 

 is equal to one degree of latitude in its effects on the climate of 



