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LI. Thoughts on thefuppofed Variations in the Axis and Poles 

 of the Earth. By ProfeJJbr Book, of Berlin'^. 



I 



T is highly worthy of remark, that, notwithftanding the 

 harmony which prevails in the courfe of the planets round 

 the fun, and in their rotation, as well as in regard to the 

 parallelifm of their axes, great variations are found in the in- 

 clination and pofition of the latter, and in the periods of the 

 rotation of thefe bodies. 



This depends on the different influence which the fun has 

 on a planet during its rotation, or the variation of its aftro- 

 romical feafons, and on the inclination of its axis in regard 

 to its orbit; for the fun, in his courfe from the one tropic to 

 the other, paffcs over an arch equal to twice the complement 

 of this inclination; and therefore .the lefs the inclination, he 

 niuft advance nearer to the poles, and employ much lefs time 

 in proceeding from the equator towards either tropic. 



Now, as it is known from obfervations that there are 

 fome planets the axes of which have a much greater or much 

 Jefs inclination than that of our earth, the great variations 

 V'hich mull naturally thence refult in regard to the beneficent 

 influence of the fun's light and heat, will give a quite different 

 nature to their fields, produftions, and inhabitants. 



The inclination of the axis of our earth, which is 66\ de- 

 grees, feems to be well adapted for promoting its fertility and 

 rendering it habitable, as the fun employs fix months in 

 moving from the equator towards either pole, and again re- 

 turning; by which means the effedl of his rays in producing 

 that heat and light fo indifpenfably neceffary to the animal, 

 vegetable, and mineral kingdom, increafes and decrcafes in a 

 much flower and gradual manner. The two temperate zones 

 occupy the greater part of the earth's furface, and thefe re- 

 main habitable as far as poffible towards either pole. 



The direction and inclination of the axes of the different 

 planets are as little proportioned to their different diftances 

 from the fun, as their periods of rotation, fize, denfily, mafs, 

 and fphcricity ; as is well known by obfervations which liave 

 been made. Novi', as there muft be fufficient grounds for 

 this arrangement, it mav be afcribed, in mv opinion, to the 

 matters of diflerent fpeciiic gravity of which the earth and the 

 other planets are compofed, and to their mixture; in confe- 

 quence of which, immediately after their formation, their 



* From Drr G,:fe!!fcbaft l^atioforfchender Freur.de s:« Berlin h'ene 

 ScbriJ'teiif vol. ii. 1799. 



hemifpheres 



