Progress of Foreign Science. 339 



very striking. The birds, and especially the reptiles, increase 

 much more towards the equatorial zone than the mammiferee. 

 According to the discoveries of M. Cuvier on fossil bones, we 

 might believe, that these proportions have not been the same at 

 all times ; and that there have disappeared, in the ancient ca- 

 tastrophes of our planet, many more mammifera than birds. 

 We can conceive how, on a given space of territory, the indivi- 

 duals belonging to different tribes of plants and animals may be 

 numerically limited; how, after an obstinate struggle and long 

 oscillations, a state of equilibrium comes to be established, re- 

 sulting from the necessities of nourishment and the habits of 

 life : but the causes which have limited the forms are hid under 

 an impenetrable veil, which withdraws from our view whatever 

 relates to the origin of things, or to the first developement of 

 organic life. 



On the preponderance of certain families of plants depends 

 the character of the landscape ; the aspect of a smiling or ma- 

 jestic nature. The abundance of gramineae which form vast 

 savannahs, that of palms and coniferse, have had a powerful 

 influence on the social conditon of nations, on their manners, 

 and the more or less rapid developement of the useful arts. 

 Sometimes a single species of plants, especially among those 

 styled, by M. Humboldt, social, covers a vast extent of country. 

 Such are, in the north, the heaths, and forests of pines; in 

 equinoctial America, the union of cactus, croton, bambusa, and 

 brathys of the same species. — The sequel of this will be given in 

 our next Number. 



Geology. — Mr. Fox having communicated to the editors of 

 the Annales de Chimie et de Physique, in a manuscript letter, 

 new determinations on the temperature of the earth at various 

 depths, these gentlemen have published them, along with an 

 extract made by M. Fourier, from his profound geometrical re- 

 searches on heat. 



The observations were made in ten different mines; viz.,— 

 Dolcoath, United Mines, Treskerby, Whealsquire, Ting-Tang, 

 Wheal-Gorland, and Wheal-Damsel (copper-mines); Chase- 

 Water (mine of tin and copper); Wheal-Unity (in the tin part 

 of the mine), and Wheal-Vor (tin-mine). The following is a 

 list of tlie temperatures observed. The numbers inscribed on 

 the table are the means of particular results obtained for each 

 depth in the ten mines above-named. 



At the depth of 10 fathoms Temp. 50.18"?.— 10.1 C. 



20 to 30 60.98 16.1 



30 to 40 .59.54 15.3 



50 to 60 62.06 16.7 



60 to 70 65.86 17-7 



70 to 80 6.0.84 18.8 



