1867.] Physics. 129 



Mr. D. Kirkaldy has published some good practical remarks on 

 the influence of repeated forging on the strength of wrought- 

 iron.* 



11. PHYSICS. 



Light. — The spectral analysis of the light of the stars has been 

 followed up unremittingly by many observers. Amongst others, 

 Father Secchi has published some generalizations : he divides the 

 Stellar spectra into three types. 



The first and most dominant type is that exhibited by white 

 stars, such as Sirius. Their characteristic is a black band in the 

 green blue, and a second band in the violet. 



Half the visible stars belong to this type. Two remarkable 

 exceptions have been found, the stars y Cassiopeise and fi Lyrae. 

 These are perfectly complementary to the type, and instead of 

 having a dark ray in the green, have a luminous band. Another 

 modification of this type is presented by the constellation Orion (a 

 excepted), which has no large bands, and in which the violet lines 

 are very difficult to see. The second type consists of stars having 

 coloured bands in the red and orange. The most remarkable 

 and typical star of this class is a Hercules, the spectrum of which has 

 the appearance of a series of columns illuminated from one side ; the 

 stereoscopic effect of the convexity of these bands, due to the 

 shading, is so surprising, that it cannot be beheld without astonish- 

 ment. The third type consists of stars giving fine lines : it 

 includes Arcturus, Capella, Pollux, &c., and also our own sun. 

 The author says that the spectra of these stars perfectly resemble 

 that of the sun, with fine fines in the same places. In these 

 stars may be seen the principal solar rays, B, I), b, E, F, G-, and 

 a great many secondary rays. 



As a proof of the existence of iron in the solar atmosphere, M. 

 A. J. Angstrom has compared the solar spectrum with one formed 

 by two iron electrodes, with a battery of 50 elements, and has found 

 more than 460 rays corresponding to the lines of iron. Two 

 observations which the author has made are of interest : one is the 

 certain presence of manganese in the sun, proved by the coincidence 

 of nearly thirty fines ; and the other is the discovery of a new 

 ray of hydrogen, situated nearly half way between Gr and H, 

 and which M. Angstrom calls h. 



An addition, which may prove important, has been made to 

 our knowledge of the obscure subject of right- and left- handed 

 polarization. 



* * Deutsche Industriezeitung,' No. 82. ' Organ fiir die Fortschritte des Eisen- 

 bahnwesens,' New Series, vol. iii., p. 178. 



VOL. IV. K 



