136 ANNUAL OF SCIENTIFIC DISCOVERY. 



panied by small strops, made with fine emery, for cleaning and pol- 

 ishing the poles previous to use, which is found to be of much conse- 

 quence. The smaller magnet has twice the power expressed by 

 Haecker's formula for the best artificial steel magnet, and even when 

 a disk of letter-paper is interposed between the poles and the keeper, 

 it will sustain the weight indicated by that formula. It will support 

 its own weight at a single pole, and in this property it resembles the 

 cylindrical bar-magnets now made in the electro-magnetic helix, and 

 used in the magnetical observatories. These magnets are manufac- 

 tured at a cheap rate, even when possessing great power. London 

 A/heii(sum, Aug. 



MAGNETIC POWER OF GLASS DERIVED FROM THE FUSION OF 



ROCKS. 



IN a paper presented to the French Academy, Jan. 28, " on the 

 magnetic power of glass produced by the fusion of rocks," M. Delesse 

 concludes that this power in glass is sometimes greater and sometimes 

 less than that of the rock from which it is derived, and, since the 

 chemical composition is nearly the same, it is evident that the mag- 

 netic power of a substance may increase or diminish without any 

 change in its chemical character. 



THE SOLAR SPECTRUM. 



AT the meeting of the French Academy, on May 13, Sir David 

 Drowsier presented a paper on the solar spectrum, in which he notices 

 particularly his observations, made during fifteen years, upon that 

 portion of the spectrum beyond the limit A of Fraunhofer, which, 

 he believes, has never been examined by any other person. This new 

 portion is about equal in length to the space between A and B. In it 

 he has detected five principal lines, and a large number of smaller 

 ones, with several bands of greater or less size, and possessing very 

 various degrees of illumination. The most remarkable portion of this 

 region of the spectrum is a group of twelve lines near A, and on its 

 least refrangible side ; they are farther and farther apart in proportion 

 as they are farther removed from A. He lias also discovered nine or 

 ten very feeble bands in the portion of the spectrum between A and B, 

 in that part of it which forms the extremity of the spectrum of Fraun- 

 hofer. From his observations, Sir David Brewster concludes that the 

 spectrum consists of an immense number of bands of different intensi- 

 ties separated by lines of different sizes. It is probable that these 

 bands are only the effects of the absorption of the atmosphere, and 

 that observations made in the higher regions of the air would give the 

 spectrum as represented by Fraunhofer, marked by distinct lines only. 

 The fact that the atmosphere has a most important effect in modifying 

 the solar spectrum does not admit of a doubt. In the spectrum formed 

 by the burning of nitre upon carbon, there are some brilliant red lines, 

 coinciding not only with the double lines A and B, but with each of 

 the eight lines composing the group a of Fraunhofer. Similar bands 



