52 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



meiits on Hansen's method of computing perturbations, in 

 that lie represents the mean anomaly of the disturbed planet 

 by an elliptic integral. By applying Gylden's and Hansen's 

 methods, Von Asten finds himself justified in the belief that 

 the complete computation of the absolute perturbations of 

 Encke's comet is a labor whose execution lies quite within 

 the limits of possibility. He has himself, in his memoir pub- 

 lished recently, gone through with the necessary computa- 

 tions relating to Jupiter's attraction on the comet, and it is 

 to be hoped that competent persons will be found to take up 

 the subject at this point, and carry out the computations re- 

 lating to the influences of other planets ; so that, eventually, 

 the question of the existence of Encke's resisting medium 

 may be definitely settled. ^U'ntersuc/mnge7i Mickeschen Co- 

 meien, Dr. Yon Asten^ St. Petersburg^ 18V2. 



ON THE COi^STITUTlON OF THE SUN's CKUST. 



Professor C. A. Young has suggested that the solar crust 

 may consist of a more or less continuous sheet of descending 

 i-ain, not of water, of course, but of the materials whose va- 

 pors exist in the solar atmosphere, and whose condensations 

 and combinations are supposed to furnish the solar heat. As 

 this tremendous rain descends, the velocity of the falling 

 drops would be retarded by the resistance of the denser gases 

 underneath, or the drops would coalesce until a continuous 

 sheet would be formed, and these sheets would unite into a 

 sort of bottomless ocean, resting upon the compressed vapors 

 beneath a forest of innumerable ascending jets and bubbles. 

 The thickness of this sheet would depend upon the evapora- 

 tion at its bottom, and upon the rapidity of its growth at the 

 top, and would probably continually increase at the same 

 slow rate. 12 A, 1873, 393. 



THE SPECTROSCOPIC METHOD OF OBSERVING THE TRANSIT OF 



VENUS. 



In order to observe the first moment of the contact of the 

 planet Venus with the disk of the sun at the approaching 

 transit of Venus, it is proposed to emplo)'^, not only the di- 

 rect photographic, but also the so-called spectroscopic meth- 

 od. This last method consists in this: Before the apparent 

 contact of the two objects takes place, a spectroscope adjusted 



