74 Intelligence and Miscellaneous Articles. 



Father Secchi writes : — " Nous acquiines la conviction que laraie 

 pouvait paraitre constamment d'un cote ou de l'autre, selon la dis- 

 position de instrument sans que l'observateur eut un indice assez 

 but pour reconnaitre rillusion dont il etait victiine." Such an illu- 

 sion was scarcely possible in the method which I employed, because 

 from the first I was careful to add to other necessary precautions, 

 that of directing frequently the telescope with the spectroscope 

 attached, to the moon, when the triple line b always coincided per- 

 fectly with the three bright lines of magnesium. When the instru- 

 ment, without any possible derangement, was again directed to the 

 star, the same displacement of the line was seen which had been ob- 

 served previously. 



It is also not necessary for me to state the special precautions 

 which have to be taken when a stellar hue " tres-large et estampee a 

 son bord " has to be compared with the bright line j3 of hydrogen, 

 because many of the comparisons were made with narrow and de- 

 fined stellar Lines with the lines of magnesium and of sodium. The 

 displacement due to the approach of Arcturus was observed not only 

 in the case of the hue F with hydrogen, but also, in the case of the 

 triple line b, with the three lines of magnesium, and the double 

 line D with the two lines of sodium. 



The observations of the displacements of lines in the spectra of 

 stars are necessarily, from their nature, of extreme delicacy ; and 

 success can be expected only when suitable care and precautions are 

 taken. 



Father Secchi says, p. 762, "M. Huggins reprit peu apres la 

 question." The application of the spectroscope to the movements 

 of the heavenly bodies was entirely original on my part. It is true 

 that Father Secchi's letter describing his negative results appeared 

 in the Comjptes Rendus for March 2, 1868, while my paper was pre- 

 sented to the Eoyal Society the following month, April 23, 1868 ; 

 but my observations for the most part, as is stated in my paper, were 

 made during the preceding year. The idea of the method was fami- 

 liar toDr. Miller and myself at the time of our comparisons of stellar 

 with terrestrial spectra in 1862-63 : see Phil. Trans. 1868, p. 529. 



ON THE INTERNAL CONSTITUTION OF MAGNETS. BY J. JAMIN. 



In a saturated magnet of infinite length, the magnetic intensities 

 y are expressed by the formula of y=Alc- x i which represents a 



curve the more elongated as 7c is smaller : - is what I have named 



the coefficient of conductivity. For one and the same quality of steel 

 in its different states A is invariable ; but the conductivity increases 

 with the annealing, and takes its least value when the steel has been 

 dipped at a white heat in cold water. If now different kinds of 

 tempered steel are compared, we find that, the higher the degree of 

 acieration, the less is this minimum of conductivity. But as the 



