314 P?vgiess of Foreign Science. 



the 7th of September, 1820 *. He employed for this purpose 

 the thermeliometre, described in the Journal cle Physique, vol. 

 Ixxxvii, p. 256. He concludes from his observations, that the ex- 

 perimental heats are equal to those calculated on the hypo- 

 thesis, that the effect of the sun-beams is proportional to the 

 extent of surface of the portion of the disc of the sun unco- 

 vered ; and of consequence that this hypothesis is the true 

 one. Whence we may infer, tliat the disc of the sun is equally 

 luminous over its whole extent, and that one part taken near 

 the centre, emanates no more rays than an equal portion taken 

 near the border of this disc. The opposite opinion was main- 

 tained by Bouguer ; who said, that if we compare by the he- 

 liometer, (an instrument of his own invention), the sun's centre 

 to a spot distant from it, by 4 of the diameter, the quantities of 

 the rays, which we receive, are in the ratio of 48 to 35. But 

 this distinguished philosopher ingenuously admits, that his expe- 

 riment contained difficulties which he had not surmounted, and 

 that it, therefore, required verification. The equality of lustre 

 now found by M. Flaugerghes, over all the parts of the disc of 

 the sun, shews, moreover, he thinks the incorrectness of the 

 geometrical hypothesis admitted by several philosophers, that 

 the portions of the surface of a body, project in all directions 

 an equal quantity of light ; for on this supposition, the lustre 

 of a spherical luminous body, ought to increase from the centre 

 to the circumference, and become even infinite at the limb ; 

 which does not take place, as we may satisfy ourselves, in con- 

 sidering an iron bullet heated to whiteness ; or a white paper 

 globe exposed to the light of day. These spherical bodies 

 will appear equally luminous over their whole surface. He 

 also infers from his observations, that the opinion of M. La- 

 place, who pretends that the sun is sorrounded with an atmo- 

 sphere such, that were it stripped of it, " this luminary would 

 appear twelve times more brilliant," is void of foundation. 



Some remarks on the temperature of mines will be found 

 under Geology. 



We shall conclude this subject for the present, by ex- 

 pressing our surprise at the ignorance of the state of English 

 science, displayed in the following introduction to a Memoir 

 of M. Despretz, read at the Institute, 29th November, 

 1819, and inserted in the 16th volume of the Annales de 

 Chimie et de Physique, p. 105: — " It is admitted with Mr. 

 Dalton, in all the works on physics, that on departing from the 

 point of ebullition under the same pressure, or for greater ge- 

 nerality, on departing from the point where the elastic forces 

 are equal, the variation in the elastic force of the vapour for a 



f Journal de Physique, torn. 93, p. 435. 



