38 General Reflections on Heat. 
chinery of the natural world were adjusted oa purpose ic 
support this equilibrium of temperature. But this happy 
adjustment was by no means accidental; we can even see 
the springs by whieh it is effected. 
Jn the first place, heat manifests the strongest tendency to 
diffuse itself in every direction. Let us concentrate it in 
any given spot, and it flies off with inappreciable velocity ; 
and, unless the intensity be maintained by constant additions 
of heat, that spot or body shortly becomes reduced to the 
same temperature with surrounding bodies. Upon this agent 
itself, therefore, is impressed a character, that restrains the 
violence which it seems constantly prone to exercise. 
In the second place, the arr, by its elasticity, affords the 
means of conveying off all excesses of beat. This cause 
operates in maintaining the equilibrium of temperature on a 
most extensive scale. We see its action, at one time, in 
gentle gales and breezes; at another, in the northern blast; 
at another, in dreadful hurricanes, that sweep around this 
solid ball. All these, whatever partial evils they involve, 
contribute to this grand benevolent design; to keep the 
vaging element of fire within its own narrow bounds. 
Fn the third place, the vast collections of water, which 
cover so great a part of the globe, furnish another means of 
regulating the temperature of the earth So happily does it 
conduce to this object, that were the art of navigation stil] 
unknown, we might fancy that lakes and seas and oceans, 
were made on purpose to be reservoirs of heat in winter, 
and fountains of cool breezes in summer. The multiform 
changes of state which water undergoes, including congela- 
tion and liquefaction, evaporation and condensation, are all 
made subservient to the same end. These operations are 
the special barriers whieh Providence has set on the terres- 
trial part of the globe to check sudden excesses of heat and 
cold; and few instances of the proofs of intelligent design in 
the works of creation, among all those happy illustrations 
which Dr. Paley has collected, ever struck me as more con- 
vineing than these. On the approach of a cold night, it is 
pleasing to watch the thermometer and note the progress of 
its descent. Perhaps asudden change of weather has caught 
the mercury ata high degree You may see it descend 
vapidly to the freezing point; and, were you unaccustomed 
to the result, you might imagine that a most terrible frost was 
st hand. But the mercury no sooner reaches the freezing 
