EARTH. 



393 



he (Mr. Calderon) would be exceedingly glad of an op- 

 portunity to gire them their 40,000 and have the 

 treatr back again. 



Mr. Calderon asked me if I supposed the recent 

 treaty would be ratified by the American Senate. I 

 replied I had no reasonable doubt that it would be, and 

 remarked that I supposed that England was now tak- 

 ing steps to obtain the same concession from the gov- 

 ernment of France. 



Mr. Calderon said he had little doubt of it, but he 

 wished to see the American treaty, as it might afford 

 a basis for demanding a revision of the Spanish treaty 

 as to the manner in which this right was to be exer- 

 cised. 



The remainder of this voluminous corre- 

 spondence is occupied with subjects of less in- 



terest. The volume is a proof of the vast la- 

 bors of the Department of State, which has 

 been conducted during the year with great 

 ability and success, in preserving the peaceful 

 and most friendly relations with foreign nations. 

 DRURY BLUFF is situated seven miles be- 

 low Richmond on the James river. It is in a 

 commanding position, owing to the curve of 

 the river, and was strongly fortified to prevent 

 the approach of the Federal gunboats to Rich- 

 mond. An attack was made upon it by the iron 

 clad Galena and several gunboats, which were 

 severely handled and retired. (See NAVAL 

 OPEBATIOXS.) 



E 



EARTH. Among the scientific deductions 

 and speculations respecting our planet, put 

 forth during the year, are some which would 

 seem likely to lead to very considerable modi- 

 fications of the views for some time entertained 

 in regard to its constitution and behavior as a 

 physical globe, and more especially in regard 

 to the condition of its interior mass. 



JSelatite Sunshine of Different Zones. Prof. 

 Hennessy, speaking before the British associa- 

 tion on this subject, called attention to the 

 fact that by means of transformation of a 

 mathematical formula of Poisson, the area of 

 that portion of the earth's equatorial regions 

 which receives as great an amount of sunshine 

 as all the rest of the surface, is readily ascer- 

 tained. This area is found to b'e that which is 

 bounded, at the outer limits of the earth's at- 

 mosphere, by parallels distant 23 44' 40" on 

 each side of the equator. Since such parallels 

 lie very slightly without the tropics, it follows 

 that the amount of sunshine falling on the 

 outer limit of the atmosphere, between the 

 tropics, is very nearly equal to that falling 

 upon the atmosphere corresponding to the 

 entire remaining portion of the earth. Now, 

 the researches of Prof. Forbes have shown that 

 the portion of the sun's heat extinguished by 

 the atmosphere during passage through it of a 

 given solar ray. and before it reaches the sur- 

 face of the globe itself, exceeds one half for 

 all inclinations of the ray to the surface less 

 than 25 ; and that for inclinations of 5, only 

 about 2 \,th part of the heat reaches the ground". 

 The torrid zone, accordingly, must receive the 

 action of by far the greater part of the sun's 

 heat; and it will follow that the distribution 

 of the absorbing and radiating surfaces within 

 such zone must exercise an influence the extent 

 of which is not usually suspected, in modifying 

 the climates of all parts of the earth's surface. 



Extent of the Earth's Atmosphere. Prof. 

 Challis, before the same body, argued that the 

 earth's atmosphere could not extend so far as 

 to the moon, since, in case it did so, some por- 

 tions of it must attach themselves by gravita- 



tion to that satellite, and these having connec- 

 tion through friction with the rest, there 

 would result a continual drag upon the earth's 

 surface, retarding its rotation. If, then, the 

 earth's rotation be uniform, its atmosphere 

 cannot extend so far as in any degree to be 

 drawn to the moon. Undoubtedly, as gener- 

 ally supposed, the atmosphere terminates at 

 some height not very great, and abruptly ; that 

 is, with a definite boundary or surface, at which 

 it has a small but finite density, and beyond 

 which there are no more atmospheric particles. 

 From considerations drawn from the rate of 

 decrease of density in ascending from and near 

 to the earth's surface, this height is usually 

 placed at about TO miles. 



Thickness of the Earth's Crust. Led chiefly 

 by the phenomena of thermal springs, of earth- 

 quakes and volcanoes, together with the ob- 

 served rise of temperature in descending in 

 mines and the boring of artesian wells, and 

 connecting with these the appearances of the 

 lower or unstratified rocks, and the interpre- 

 tation given to all the facts by -Laplace's nebu- 

 lar hypothesis, geologists have for many years 

 past become pretty generally agreed in regard- 

 ing our globe as still possessing but a thin solid 

 crust enveloping an intensely hot and molten 

 core; and from calculations of the depths at 

 which the metals and finally the most refrac- 

 tory rock materials must melt, the thickness 

 of such crust has been supposed no greater 

 than 100, 70, and by some even 30 miles. 

 Within a very few years, however, objections 

 to this theory, or at the least to that of such 

 extreme thinness of solid earth, have sprung 

 up in different and unexpected quarters. About 

 three years since, the Rev. J. H. Pratt, residing 

 at Calcutta, end to whom the immense quantity 

 of matter piled up in the long and massive 

 Himalayan chains had become a very patent 

 fact, published his views to the effect that, 

 through differing pressures at near parts of the 

 crust, where the weight of chains like the 

 Himalayas is far under-balanced by the dimin- 

 ished pressure on ocean bottoms, while the 



