Intelligence and Miscellaneous Articles. 233 



which are given in the first column under B. Accordingly, for 

 angles greater than those given, the above Tables hold good. 



Precisely the same phenomena as on the ground and polished salt 

 may be observed on crystals. Just so are they exhibited on per- 

 manganate of ammonia ; but here measurements were impossible, 

 on account of the great decomposability of the salt. 



The above observations were verified in every way possible. For 

 example, the dependence of the situation of the streaks on the index 

 of refraction was again established by putting benzine and sulphide 

 of carbon in layers one above another, immersing a glass plate 

 coated with polished permanganate of potassium, and comparing 

 immediately the spectra of the light reflected at the boundaries of 

 the two media by the permanganate. The streaks in the spectrum 

 of the light which had passed through the sulphide of carbon were, 

 in relation to those in the spectrum of that which had traversed 

 the benzine, displaced towards the blue. — PoggendorfPs Annalen, 

 1874, No. 4, pp. 625-628. 



ON THE TEMPERATURE OF THE SUN. BY J. VIOLLE. 



I have previously indicated and discussed the method I most 

 frequently employ in my measurements concerning the temperature 

 of the sun. I shall today describe the apparatus I use, and shall 

 develop the calculus of the experiments. 



My apparatus is composed of two concentric spherical envelopes 

 of brass. The interior one, 15 centims. in diameter, constitutes 

 the enclosure, in the centre of which is the bulb of the thermometer 

 submitted to experiment. This enclosure, blackened on the inside, 

 is kept at a constant temperature by a continuous current of water 

 furnished by the conduit-pipes of the city and circulating between 

 the two balls. The exterior ball has a diameter of 23 centims. ; it 

 has been carefully polished on its outer surface, and is, besides, 

 protected by screens which leave free only the admission-aperture. 

 This aperture is at one of the extremities of a brass tube 17*5 mil- 

 Ems, in diameter, directed along one of the radii of the sphere, and 

 opening at the other end into the inner ball. The free extremity 

 of the admission-tube carries a movable diaphragm pierced with 

 three circular apertures of different sizes. Three other tubes tra- 

 verse, in radial directions, the space comprised between the two 

 spheres : two of them, placed one at 45°, the other at 90° from the 

 admission-tube, serve, the one or the other according to circum- 

 stances, to give passage to the stem of the thermometer; the third, 

 closed by ground and slightly blackened plate glass, is directed 

 along the prolongation of the admission-tube, and permits the 

 ascertaining that the solar rays fall exactly on the bulb of the ther- 

 mometer. The suitable orientation of the apparatus is, besides, 

 attained without difficulty, thanks to its spherical form, which per- 

 mits it to be turned gradually in the wished-for direction upon a 

 circular ring which serves as its support. 



