A. MATHEMATICS AND ASTRONOMY. 9 



familiar with the generalization of Hadley, viz., that the un- 

 der-cuiTents of our atmosphere sweep along the surface of 

 the earth from the poles to the equator, Avliile upper currents 

 return from the equator to the poles. These are caused by 

 the unequal temperatures of the respective portions of the 

 earth. They therefore have a reference, not so much to the 

 geographical equator and poles, as to the hottest and coldest 

 regions. These currents have both annual and daily oscilla- 

 tions. On the other hand, the earth is a magnet, and the ex- 

 istence of these general currents in our atmosphere suggests 

 an explanation as to the origin of terrestrial magnetism. 

 We bear in mind that rarefied air is a good conductor of 

 electricity. The return trades that pass above from the 

 hotter equatorial regions to the poles of cold, consisting of 

 moist, rarefied air, are therefore to be regarded in the light 

 of good conductors crossing the so-called lines of magnetic 

 force. They therefore are the vehicle of electric currents, 

 such as will of course react upon the magnetism of the earth ; 

 and there is, according to Stewart, a similarity between the 

 peculiarities of the magnetic variation and the annual and 

 daily variations of the winds, such as invites a further scru- 

 tiny. A similar parallelism exists apparently when we com- 

 pare the storms in the atmosphere with the magnetic storms 

 recorded by the needle. Balfour SteioarVs Address at Bris- 

 tol, 1875. 



CONFLICTING VIEWS OF SECCHI AND LANGLEY IN REGARD 



TO THE SUN. 



Professor Langley, of the Alleghany Observatory, having 

 lately published in the American Journal of Science, and the 

 Meniorie degli Spettroscopisti Italiani, an article on the "Com- 

 parison of Theories of Solar Structure with Observation," in 

 which certain supposed views of Father Secchi, of Rome, were 

 referred to, the latter has replied at length in subsequent num- 

 bers of the Italian journal, commenting upon the researches 

 of the American observer, and explaining his own views in 

 such a way as to lead us to suspect a sudden conversion to 

 views opposed to those he has advocated for so many years. 



Father Secchi states his present view, which is, briefly, as 

 follows, that a sun-spot is the product of an eruption on the 

 sun, somewhat analogous to that of a terrestrial s'olcano. 



A 2 



