l&l 



absorb its luminous particles, in a manner nearly similar to that 

 which Dr. Herschel has supposed to take place with regard to the 

 sun's atmosphere. 



4thly. That as the variable star in Sobieski's Shield is occasionally 

 diminished in appearance to the 6th or 7th magnitude, or even to a 

 smaller magnitude, it appears that these luminous particles are but 

 sparingly dispersed in its atmosphere. 



5thly. He asks, may we not with much plausibility represent such 

 luminous particles as spots, somewhat circular, and of no great ex- 

 tent. 



6thly. That the principal bright parts are but slight patches, may, 

 he says, be presumed, from the perpetual changes they undergo, and 

 also from such changes being very visible to us. 



7thly. He thinks we may obtain some idea of the relative situation 

 or intervals between these bright parts, by the observations of the 

 increase and decrease of brightness, as thereby the changes and times 

 elapsed are pointed out. 



Mr. Pigott says he has tried, practically, the effect of the above 

 suppositions, by placing small white spots on a dark sphere, which 

 sphere being turned round, represented the various changes as nearly 

 as could be expected. Of these changes several views are given, ac- 

 companied with some observations on variable stars in general ; in 

 the course of which the author supposes it probable that many stars 

 have lost their light, and that there are many others which have never 

 shown a glimpse of brightness. He even asks, whether we may not 

 suppose the number of these unenlightened stars equal to that of 

 those endowed with light ? If so, he thinks that by being collected 

 together in clusters, as in the Milky Way, they must intercept all 

 more distant rays ; and if free from any intervening lights, must ap- 

 pear as dark spaces in the heavens, similar to what has been observed 

 in the southern hemisphere. 



Mr. Pigott, at the conclusion of his paper, says he thinks there are 

 strong reasons to believe that the sun's luminous appearance has been 

 at times considerably diminished ; also, that he has little hesitation 

 in conceiving it may, at some future period, be reduced to small 

 patches. 



An Account of some analytical Experiments on a mineral Production 

 from Devonshire, consisting principally of A lumine and Water. By 

 Humphry Davy, Esq. F.R.S. Professor of Chemistry in the Royal 

 Institution. Read February 28, 1805. [PAzV. Trans. 1805, p. 155.] 



The mineral, of which an account is here given by Mr. Davy, was 

 found many years ago by Dr. Wavel, in a quarry near Barnstaple. 

 It was then considered as a kind of zeolite ; but Mr. Hatchett, who 

 visited the place in the year 1796, describes it as filling some cavities 

 and veins in a rock of soft argillaceous schistus ; and from that cir- 

 cumstance concluded, that it most probably did not belong to the 



