180 Scientific Intelligence. 



8. The Double Star 61 Cygni. — It appears that M. Arago has lately at- 

 tempted, in vain, to discover a sensible parallax in this remarkable double 

 star. Dr Brinkley, long ago, (see his Elementary Treatise of Astronomy,) 

 observed this star for the same purpose, but found no parallax in declina- 

 tion. Professor Bessel obtained a negative parallax, seeming to show that 

 it was more distant than the stars with which he compared it. The ra- 

 pid motion of this pair of stars, would certainly induce us to believe them 

 nearer than other stars ; but the notion, when examined, appears to be 

 no better supported than the commonly received one, that the brightest 

 stars are nearest to us. — Dublin Phil. Journal, No. ii. p. 450.J 



OPTICS. 



*9. Effect of the Sun's light in diminishing Combustion. It has always 

 been considered a vulgar error, that the sun's light extinguishes a fire, but 

 the following experiments by Dr M'Keever put the matter beyond a doubt. 

 See Ann. of Phil. x. 344. 



I. A green wax taper in sunshine lost 8£ grains in five minutes. 



A white wax taper in a darkened room lost 4£ — — 



8. In bright sunshine a piece of wax taper 7 inches long required to 

 consume it 5' 0" 



In day light it required - 4 52 



In a dark room - 4 30 



3. In the spectrum one inch of taper was burnt in the following 

 times : 

 At the end of the violet ray 

 In the centre of the violet ray 

 In the centre of the green ray 

 In the centre of the red ray 



10. Singular Phenomenon observed by M. Ramond on the Pic du Midi. 

 — When M. Ramond was on the Pic du Midi, he observed his own sha- 

 dow, and those of his two companions, projected on a cloud situated a little 

 distance above them, with a distinctness and an accuracy of outline quite 

 surprising; but what was more astonishing, these shadows were encircled 

 with glories, shining with the most brilliant colours. " Those who witnessed 

 this magnificent spectacle," says M. Ramond, " might have supposed that 

 they were assisting at their apotheosis." Several naturalists, among others, 

 Bouguer, and the sons of Saussure, have seen this phenomenon ; but none 

 of them observed this distinctness of form, which can only be explained 

 by the smoothness of the surface of the cloud upon which the shadow was 

 projected. With respect to the glory, Bouguer supposed that it might 

 arise from the decomposition of the light produced by the particles of ice 

 suspended in the cloud. Thus he would say, that the rays of the sun 

 beino- intercepted at the place occupied by the shadow, there is produced 

 at the place a coldness, and the icy particles becoming more numerous 

 there, and on the margin of the shadow, produce the decomposition of the 

 light. M. Ramond, however, objects to this explanation, and considers 

 it as certain, that the cloud on which his shadow was projected could not, 

 from the temperature of the Pic, have then held any icy particles in sus- 

 pension. 



