VOL. XLI.l 1>HIL080PHICAL TRANSACTIONS. 371 



windward of us for 3 or 4 miles, showered ashes plentifully upon us, and we lost 

 our sinell of every thing but brimstone. All the trees, vines, and hedges, 

 bent under the weight of these ashes; several arms, and even bodies of trees, 

 were broken with the weight ; so that in some narrow roads we had difficulty 

 to pass. Within a mile or two of the prince of Ottaja no's palace, one can 

 scarcely frame to one's self a sight of greater desolation ; 10 successive north- 

 ern winters could not have left it in a worse condition ; not a leaf on a tree, 

 vine, or hedge, to be seen all the way we went, and some miles further, as we 

 were informed. Here, and at the town, they had a new earth, about 2 feet 

 deep, some said more, by the account of the miserable inhabitants, who were 

 a dismal spectacle. The storm fell so thick and heavy for that time, that they 

 almost all fled, and many houses were beaten down. In one convent, two or 

 three nuns were buried in the ruins. At Somma, on the north-east side, it 

 has made great havock ; a monastery of nuns was destroyed. After a long day's 

 work, we returned at six o'clock. 



Of the Lunar Atmosphere. By M. Jean Paul Grandjean de Fouchy, of the 

 Royal Academy of Sciences at Paris. N° 455, p. 26 1. Translated from the 

 Latin. 



By an atmosphere is meant a certain assemblage of pellucid matter surround- 

 ing the planet, and capable of turning the rays of light, that pfTss through it, 

 from a right lined course. M. F. does not here inquire what may be an atmo- 

 sphere, in other respects, different from that of a refracting medium, but only 

 undertakes to prove, that the moon is not enveloped by any thing capable of 

 refracting the rays of light. He conceives an atmosphere, in this inquiry, to 

 be a homogeneous fluid, with a spherical surface, of a uniform density, which 

 is equal to the sum of the decreasing densities in the real atmosphere ; pur- 

 posely omitting the difference of density in the parts, as not disturbing the de- 

 monstrations. 



Now if the moon be encompassed with an atmosphere, its diameter ought to 

 be found greater than in the naked planet. And that the quantity of the in- 

 crease may be known, let a i b, fig. 3, pi. 8, be the body of the moon, peg 

 its atmosphere ; then the angle a h l will be that of the real diameter of 

 the moon, and the angle e h l, made by the axis l h, and the ray a e h, 

 will be the observed diameter : so that the angle e h a will be the increase 

 of the moon's diameter by the atmosphere. But the angle e h a is opposite 

 to the side e a, of the triangle eh a; and the angle a e h, the supplement 

 to I80° of the horizontal refraction in the lunar atmosphere, is opposite to the 



3b 2 



