HEAT. 



321 



the tropics, or exploring the rigors of the poles, we are ever under its influence. 

 We are at once its slaves and its masters. 



We are its slaves : Without it we cannot for a moment live. Without its 

 well-regulated quantity we cannot for a moment enjoy life. It rules our pleas- 

 ures and our pains ; it lays us on the sick bed, and raises us from it. It is our 

 disease and our physician. In the ardor of summer we languish under its ex- 

 cess, and in the rigor of winter we shiver under its defect. Does it accumu- 

 late around us in undue quantity, we burn with fever; does it depart from 

 us with unwonted rapidity, we shake with ague ; or writhe under the pains of 

 rheumatism, and the tribe of maladies which it leaves behind when it quits us. 



We are its masters : We subdue it to our will and dispose it to our pur- 

 poses. Amid arctic snows we confine it around our persons, and prevent its 

 escape by a clothing* impervious to it. Under a tropical sun we exclude it by 

 like means. We extort it from water to obtain the luxury of ice in hot seasons, 

 and we force it into water to warm our apartmentsf in cold ones. Do we trav- 

 erse the seas it lends wings to the ship, and bids defiance to the natural op- 

 ponents, the winds and the tides. Do we traverse the land it is harnessed to 

 the chariot, and we outstrip the flight of the swiftest bird, and equal the fury 

 of the tempest.;}; 



If we sleep, our chamber and our couch are furnished with contrivances for 

 its due regulation. If we eat, our food owes its savor and its nutrition to heat. 

 From this the fruit receives its ripeness, and by this the viands of the table 

 are fitted for our use. The grateful infusion which forms our morning repast 

 might remain for ever hidden in the leaf |[ of the tree, the berry of the plant, or 

 the kernel^! of the nut, if heat did not lend its power to extract them. The 

 beverage that warms and cheers us, when relaxed by labor or overcome by fa- 

 tigue, is distilled, brewed, or fermented, by the agency of heat. The produc- 

 tions of nature give up their sanative principles to this all-powerful agent ; and 

 hence the decoction or the pill is produced to restore health to the sinking 

 patient. 



When the sun hides his face and the heavens are veiled in darkness, whence 

 do we obtain light ? Heat confers light upon air, and the taper burns and the 

 lamp blazes,** producing artificial day ; guiding us in the pursuits of business or 

 of pleasure, and thus adding to the sum of life, by rendering hours pleasant 

 and useful which must otherwise have been lost in torpor or in sleep. 



These, and a thousand other circumstances, prove how important a physical 

 agent is that to the explication of whose effects the pages of the present dis- 

 course are devoted. But it is not alone the intrinsic importance of the sub- 

 ject, nor its connexion with every natural appearance that can attract observa- 

 tion or excite inquiry, which has induced us to examine it. It presents other 

 advantages which merit peculiar consideration, with a view to popular instruc- 

 tion. 



The phenomena all admit of being explained without the aid of abstruse 

 reasoning, technical language, or mathematical symbols. The subject abounds 



* Clothing, in general, is composed of non-conducting substances, which in cold weather prevents 

 the heat produced by the body from escaping, and preserves its temperature; and in hot weather 

 excludes the heat from the body, so as to prevent unrtue warmth. 



t Buildings are warmed by hot water carried through the apartments in pipes. 



i The swiftest flight of a carrier pigeon does not exceed the rate of twenty-six miles an hour. It is 

 calculated that the velocity of a high wind is at the rate of about thirty to thirty-five miles an hour. 

 The steam-carriages on the Manchester and Liverpool Railway have been known to travel about 

 six-and-thirty miles an hour ; and it is slated, in the evidence before a committee of the House of 

 Commons, that steam-carriages have run on common roads at a speed exceeding forty miles an hoar. 



|j The tea-tree. 



$ Coffee. 



IF Chocolate. 



"** Flame is gas, or air, rendered so hot as to become luminous. 



21 



