Astronomy. 169 



relation which the fusing point of pure silver bears to the ordinary ther- 

 mometric scale. A full account of these proceedings, which was read be- 

 fore the Royal Society of London, will probably appear in the next volume 

 of their Transactions. 



9. Method of making Ultramarine, discovered by M. Tunel. 

 This most important discovery, which will give the greatest satisfac- 

 tion to painters and all the lovers of the fine arts, was announced to the 

 Academy of Sciences in February last. The fortunate discoverer of this 

 process, which will very properly be kept secret for some time, was made 

 by M. Tunel, inspector of gunpowder and saltpetre. It was by following the 

 analysis of M. Clement Desormes that he succeeded in the direct formation 

 of it, and what he obtains is actually finer and more brilliant than the 

 natural colour. M. Tunel has already been able to supply the public with 

 ultramarine at one guinea per ounce, the ,colour having hitherto been sold 

 from two guineas to two pounds ten shillings per ounce. He expects, how- 

 ever, to be able to sell it at a more moderate price. Le Globe, Fev. 9, 1 828. 



Art. XXVIL— SCIENTIFIC INTELLIGENCE. 



I. NATURAL PHILOSOPHY. 

 ASTRONOMY. 



1. Spots on the Sun. — Towards the middle and end of May 1828, the sun 

 appeared covered with a very unusual number of spots, one of them of ex- 

 traordinary size. On the 23d, when I observed it with great care, it was near- 

 ly in the centre of its path across the sun's disc, when I estimated the penum- 

 bra at -fa of the sun's diameter in breadth, which gives about 1' 6" for the 

 angle which it subtended and near 31,000 miles for its absolute extension. 

 The dark nucleus of the spot was not uniform and unbroken, when examin- 

 ed witli a considerable power : it appeared, especially towards the edges, 

 composed of smaller spots in a state of aggregation, and forming pretty near- 

 ly a square rounded off at the corners, of which form the penumbra closely 

 partook, except that at one point it stretched out considerably to the west and 

 included three minute spots in that direction ; but this partial extension was 

 not counted in the preceding measurements. * Yet this formed only one of 

 seven points on the sun's surface in which spots were distributed, in some 

 places single spots, in others groups of three and upwards. In all, there 

 were at least 22 or 23 spots visible on the disc, — a sight very rare and ex- 

 tremely interesting. Cloudy weather has generally prevented me from pur- 

 suing farther my observations. The weather was particularly warm dur- 

 ing the continuance of these spots, as I also observed to be the case with 

 the great spots of June 1826. See this Journal, Number x. p. 245. 



June 6, 1828. A 



2. M. Damoiseau on Enckes periodical comet. — M. Damoiseau has 



