20G

LECTURE V.

On the Nature and Constitution of the Atmosphere ;and its Influence on Vegetables. Of the Germina-tion of Seeds. Of the Functions of Plants intheir different Stages of Growth ; with a generalView of the Progress of Vegetation.

The constitution of the atmosphere has beenalready generally referred to in the preceding Lec-tures. Water, carbonic acid gas, oxygene, andazote, have been mentioned as the principal sub-stances composing it; but more minute enquiriesrespecting their nature and agencies are necessaryto afford correct views of the uses of the atmospherein vegetation.

On these enquiries I now propose to enter ; thepursuit of them, I hope, will offer some objects ofpractical use in farming ; and present some philo-sophical illustrations of the manner in which plantsare nourished ; their organs unfolded, and theirfunctions developed.

If some of the salt called muriate of lime thathas been just heated red be exposed to the air, evenin the driest and coldest weather, it will increase in3