CaNTo 1 VNEGETATLON. 13

With äiry lens the ſcatter'd rays aſſault,

And bend the twilight round the duſky vault;

ence, and the lighter will in conſequence be found round the aRXIS, 3. Ihere may be a place at ſome certain latitude between the poles and the line on each ſide the equator, where the in- flammable ſupernatant atmoſphere may end, owing to the greater centrifugal force of the heavier aerial atmoſphere. 4. Between the termination of the aerial and the beginning of the gaſſeous atmoſphere, the airs will occaſionally be intermixed, and thus become inflammable by the ele&ric ſpark; theſe circumſtances will aſliſt in explaining the phenomena of fire balls, northern

lights, and of ſome variable winds, and long-continued rains.

Since the above note was firſt written, Mr. Volta I am'in- formed has applied the ſuppoſition of a ſupernatant ätmoſphere of inflammable air, to explain iome phenomena in meteorology. And Mr. Lavoiſier has announced his deſign to write on this ſubject. Traite de Chimie, Tom. 1. lam happy to find theſe opinions ſupported by ſuch reſpeCtable authority.

And bend the twilight. 1. 126. The crepuſcular atmoſphere, or the region where the light of the ſun ceaſes to be refracted to us, is eſtimated by philoſophers to be between 40 and 50 miles high, at which time the ſun is about 18 degrees below the ho- rizon; and the rarity of the air is ſuppoſed to be from 4,000 to 10,000 times greater than at the ſurface of the earth. Cotes's Hydroft. p. 122. The duration of twilight differs in different ſeaſons and in different latitudes; in England the ſhorteft twi- light is about the beginning of October and of March; in more northern latitudes, where the ſun never fſinks more than 158 de- Srees, below the horizon, the twilight continues the whole

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