492 I'HILOSOPHICAL TRANSACTIONS. [aNNO 1795. 



at all. The same remark may be made, with regard to the number of very close 

 double stars; whose apparent diameters being alike, and not very small, do not 

 indicate any very great mutual distance. From which, however, must be deducted 

 Jill those where the different distances may be compensated by the real difference 

 in their respective magnitudes. 



To what has been said may be added, that in some parts of the milky way, 

 where yet the stars are not very small, they are so crowded, that in the year 

 1792, Aug. 22, I found by the gages, that in 41 minutes of time, no less than 

 258 thousand of them had passed through the field of view of my telescope. It 

 seems therefore, on the whole, not improbable that, in many cases, stars are 

 united in such close systems as not to leave much room for the orbits of planets, 

 or comets; and that consequently, on this account also, many stars, unless we 

 would make them mere useless brilliant points, may themselves be lucid planets, 

 perhaps unattended by satellites. 



Postscript. — The following observations, which were made with an improved 

 apparatus, and under the most favourable circumstances, should be added to those 

 which have been given. They are decisive with regard to one of the conditions 

 of the lucid matter of the sun. 



Nov. 26, 1794, 8 spots in the sun, and several sub-divisions of them, were all 

 equally depressed. The sun was every where mottled. The mottled appearance 

 of the sun was owing to an inequality in the level of the surface. The sun was 

 equally mottled at its poles and at its equator; but the mottled appearances may 

 be seen better about the middle of the disc than towards the circumference, on 

 account of the sun's spherical form. The unevenness arising from the elevation 

 and depression of the mottled appearance on the surface of the sun, seemed, in 

 many places, to amount to as much, or to nearly as much as the depression of 

 the penumbrae of the spots below the upper part of the shining substance; with- 

 out including faculae, which were protuberant. The lucid substance of the sun 

 was neither a liquid, nor an elastic fluid; as was evident from its not instantly 

 filling up the cavities of the spots, and of the unevenness of the mottled parts. 

 It exists therefore in the manner of lucid clouds swimming in the transparent at- 

 mosphere of the sun; or rather of luminous decompositions taking place within 

 that atmosphere. 



IK uin Account of the late Eruption of Mount Vesuvius. By the Right Hon. 



Sir W. Hamilton, K. B., F. R. S. Dated Naples, Aug. 25, 1794- p. 73. 



All great eruptions of volcanos must naturally produce nearly the same pheno- 

 mena, and in Serao's book on the eruption of Vesuvius, of 1737j almost all the 

 phenomena we have been witness to during the late eruption of Vesuvius, are 

 there admirably described, and well accounted for. The classical accounts of the 



