388 Transactions. — Miscellaneous. 



on an object from the outside cannot affect that object as a 

 whole under exactly the same conditions, whether the object 

 be moveable or the reverse. The sun acts on the earth 

 daily, and, indeed, momentarily, but each moment a different 

 portion of the surface comes under the influence of the sun'a 

 rays. The circle of illumination to-day on the earth's surface, 

 though the same in size or bigness as it was yesterday, is not 

 the same m position, and to-morrow's circle will be different 

 from to-day's. The angle of incidence of the earth in rela- 

 tion to the sun varies every moment as the earth moves in its 

 ecliptic round the sun. Were the earth to present a vertical 

 plane surface to the sun the same number of heat-rays would 

 fall equally over each degree of latitude. Everywhere the 

 rays would reach the earth at the same incidence, and, coming 

 from the same source, the same surface temperatures would 

 result. 



But this is what does not take place. The earth's surface 

 is rounded, and during its revolutionary movement about the 

 sun a special area of it is constantly being brought within its 

 immediate influence. This area is the torrid zone, and it is 

 this area that receives, space for space, more rays than any 

 other portion of the earth's surface, for the nearer the area to 

 the torrid zone the more heat-ravs are received from the sun 

 compared with any similar area more remote. Thus the cir- 

 cumpolar area, if compared with a similar area within the 

 torrid zone, would receive much less heat from the sun, owing 

 to the absorption of such rays by the atmosphere. Within 

 the torrid zone the estimate is made that about 8 per cent, of 

 the heat-rays which would otherwise reach the earth are ab- 

 sorbed by the atmosphere on their way, whilst 83 per cent, of 

 heat-rays are absorbed within the polar and circumpolar areas. 

 In other words, taking area for area within the torrid and 

 frigid zones, about 92 per cent of the heat-rays from the sun 

 fall upon the surface in the former, and only 17 per cent, in 

 the latter. The results under such conditions must neces- 

 sarily produce wide contrasts in the physical conditions exist- 

 ing, more especially in the case of moving water and the 

 water-products, rain, ice, snow. 



The temperature of the waters within the torrid zone may 

 be set down at 80°, for, according to Wharton, it is 78° in tlie 

 Atlantic and 82° in the Pacific, whilst the temperature within 

 the frigid zone is certainly less than 32°. Curiously, below 

 800 fathoms the temperature is never more than 35° in the 

 torrid zone, and may be set down at 30° in the frigid, al- 

 though recent tests show that a higher temperature prevails 

 than this, even at 2,000 fathoms, in the Arctic Ocean. The 

 argument, however, which it is desired to enforce is not 

 affected thereby. The difference in temperature of the 



