480 TEE ICE A QE IN NORTH AMERICA. 



we do not know in how far the loss of heat is impeded, even an 

 accurate knowledge of the temperature of space would be of 

 small use in this matter. I will illustrate this by a homely 

 example. Take a room where the fire is extinguished and the 

 hearth or stove cold in the evening, and try to guess at the 

 temperature the room will have in the morning. If we follow 

 the method of Dr. Croll, we should inquire only about the out- 

 side temperature, and not about the thickness of the walls, the 

 windows, etc. I think that, taking the average construction 

 of Russian, English, and Italian houses, if the inside tempera- 

 ture was in all three cases 60° in the evening, and the outside 

 temperature 20° in Eussia, 32° in England, and 45° in Italy, 

 the morning temperature in the room would not be very differ- 

 ent, and probably even higher in the Russian room, owing to 

 its thick walls, double windows, etc. . . . 



Thus it is easy to see that the question how great will be 

 the temperature of the air at a given place, say in midwinter, 

 when the distance of the sun is greater or less than at present, 

 can not be answered, even approximatively, especially in the 

 exceedingly crude way it is put by Dr. Croll — that is, without 

 distinguishing high and low latitudes, continent and ocean, 

 etc. One thing is certain, that such a change will certainly 

 have a greater influence on the temperatures in the interior of 

 continents than on the oceans and their borders. The caloric 

 capacity of water is so great, and the mobility of its particles 

 so effectual in resisting a lowering of the surface temperature, 

 by the convection currents it causes, that I doubt very much 

 if, during a great eccentricity and winter in aphelion, the sur- 

 face temperature of the oceans can be lower in winter than 

 now ; the difference in the quantity of sun-heat is too small 

 and too short-continued to give an appreciable difference in 

 winter ; and, as in the year there is no difference in the quan- 

 tity of heat received by the waters, I think there will be no 

 difference in the temperature of the waters, and thus no influ- 

 ence of great eccentricity with winter in aphelion on the ocean 

 temperatures, and also no greater snow-fall than now. As to 

 the continents, I admit that, though we are unable to calculate 

 the rate of decrease of temperature of the winter months in these 

 conditions, there is no doubt that it will he appreciable, and be 



