ed General Heflections on Heat. 
matter, without reflecting that this is also that principle by 
which r1rz itself, both animal and vegetable, is nourished and 
sustai ack, at the close of his incomparable lec- 
tures on heat, has ses this subject, in his asuat plain but 
impressive language. * Tis influence,” he observes, ‘*is mani- 
festly so universal, and its action so important and necessary 
to the progress of all the operations of nature, that, to those 
who eonsider it with some attention, it will appear to be the 
| eet material principle of all motion, activity, and life, in 
be. Heat is inseparably necessary to the existence 
pe vegetables and animals. Without it they want the power 
te attract their nourishment, or to set it in motion through 
their system, or to refine and ripen it in their different parts. 
Their vigour and life depend on its influence. It is only when 
énlivened by heat, that they make it assume the mt 
forms and qualities, which we find in the wood, the root, 
he leaves, the juices, the fruit, the seeds, and the benotifet 
forms and colours displayed in the flowers. They decay and 
die when heat departs. Nor is animal life less dependent 
en heat for es ae than vegetable. Heat is the main-spring 
in the eorporeal a of an animal, without which all motion 
and life would instan a 
After referring us te the vivifyin ‘aftadnee of heat exbie 
bited in the incubation of an egg, the same excellent author 
: © But, after the animal is thus brought into ex- 
istence, heat is still necessary for its support. If heat be di- 
minished toa certain degree, although no visible damage be 
produced, all motion and life are quickly extinguished. The 
animal is seized with a sleep and insensibility, under which 
it expires.” He goes on next to enumerate some of the 
endless changes which oecur in nature in consequence of va- 
riations of temperature, and thus concludes: “ But, in this sue- 
cession of forms and operations which water undergoes, you 
will perceive that it is set in motion and adapted to these 
ends, by the nice adjustment, and gentle vieissitudes of heat 
and cold, which attend the returns of day and night. and sum- 
mer and winter. Were our heat to be diminished, and to 
continue diminished, to a degree not far below the ordinary 
or es the water would lose its fluidity, and assume 
the of a solid hard body, totally unfit for the numerous 
which it serves at present; and, if the diminution of 
were to go still further, the air itself would lose its elas- 
ticity, and would be frozen to a solid useless matter like wa- 
