LIMITS OF HEAT AND COLD. 177 



cold in winter, and in a still greater degree, the 

 heat of the summer, depends more upon the 

 position of a place in the interior of the mainland, 

 than upon the latitude. Warm summer days are 

 met with everywhere except in the extreme north, 

 where the sun has no longer the power to melt 

 the ice and snow that has been stored up during 

 the long winter. 



Over the open sea, even in the hottest parts of 

 the world, the temperature is seldom found as 

 high as 30° C. (86° P.), and never above 31° C. 

 (87°*8 F.) It is as warm as this in some days 

 of summer at Yakutsk, although in winter at that 

 place mercury is often solid under the hammer for 

 months together. "While the changes of tempera- 

 ture on the ocean are confined within bounds of 3 or, 

 at most, 4 deg. C. (5*4 or 7*2 deg. F.), yet fluctua- 

 tions of 40 or 50 deg. C. (72 or 90 F.) are quite com- 

 mon in inland countries, especially in high latitudes. 

 At Moscow a difference of 78'4 deg. C. (141*1 F.), 

 and at Yakutsk even of 88 deg. C. (158*4 F.) have 

 been observed. Degrees of cold above — 50° C. 

 ( — 58° F.) are by no means uncommon in the most 

 northern countries ; but it does not appear that 

 -60°C. (-76° F.) has yet been observed any- 

 where in the open air. The temperature seems to 

 rise sometimes at many places to the same distance 

 above 0° C. (32° F.), as at other places it falls 

 below that point. At Suez, at the time of the 



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