189 
LECTURE V. 
ON THE NATURE AND CONSTITUTION OF THE ATMOSPHERE ; 
AND ITS INFLUENCE ON VEGETABLES. OF THE GERMIN- 
ATION OF SEEDS. OF THE FUNCTIONS OF PLANTS IN 
THEIR DIFFERENT STAGES OF GROWTH ; WITH A GENE- 
RAL VIEW OF THE PROGRESS OF VEGETATION, 
The constitution of the atmosphere has been al- 
ready generally referred to in the preceding Lec- 
tures. Water, carbonic acid gas, oxygene, and 
azote, have been mentioned as the principal sub- 
stances composing it ; but more minute enquiries 
respecting their nature and agencies are necessary 
to afford correct views of the uses of the atmo- 
sphere in vegetation. 
On these enquiries I now propose to enter ; the 
pursuit of them, I hope, will offer some objects of 
practical use in farming ; and present some phi- 
losophical illustrations of the manner in which 
plants are nourished ; their organs unfolded, and 
their functions developed. 
If some of the salt called muriate of lime that 
has been just heated red be exposed to the air, even 
in the driest and coldest weather, it will increase 
in weight and become moist ; and in a certain time 
will be converted into a fluid. If put into a retort 
and heated, it will yield pure water ; will gradually 
recover its pristine state ; and, if heated red, its 
