A Plant that Melts Ice 29 



coinbiniiij^ witli the oxygen of the air in tlicir 

 bodies. Luii,i;s, in tact, are mere devices for takiiii^ 

 ill fresh oxyj^en, which then combines with tlie 

 food or fuel in the blood of the animal. 



A centmv ai^o, Count Rumford pointed out that 

 you mi^ht biun your hay as you ciiose, either 

 in a horse or in a steam-eiii^ine ; and tiiat in 

 either case you produced alike heat and motion. 

 Wliat we call fuel is just carbon and hydroj^en, 

 separated from oxyj^en ; and wliat we call burninj^ 

 or combustion is just the re-union of the oxyj^en 

 with the other elements, accompanied by a ^ivinj^- 

 off of heat equivalent in amount to that orij^inally 

 reciuired in order to separate tiiem. 



Now, the foodstuffs of most animals are plants 

 or parts of plants, especially seeds or j4i-ains, as 

 well as the rich stores of starch or oil laid by in 

 roots, bulbs, and tubers. These are all of them 

 reservoirs of food or fuel, produced by the plant 

 for its own future growth, and meant hereafter to 

 sprout or j^erminate. All seeds, when they be^in 

 to ejuicken, unite with oxygen and evolve heat ; 

 and this heat is just the same in nature, whether it 

 happen to be set free within or without an animal 

 body. If you give an ox corn, he will oxidise it 

 internally and warm his own body with it ; but if 

 you let it j^erminate, it will oxidise itself, and so 

 produce a very small but slow lire, which warms 

 both the corn and the space around it. Similarly, 

 all growing shoots combine with oxygen, and, 

 therefore, rise in temperature. In early spring, 

 when the ground just teems with sprouting seec! , 



