THE VEGETABLE KINGDOM. 393 



duces. Mariotte tried a very elementary experiment on 

 this head. Having cut off a branch and covered the section 

 with impermeable cement, he observed that the leaves, 

 while withering, had lost two teaspoonfuls of water in two 

 hours, at a time when the air was tolerably warm. The 

 naturalist therefore concluded that in twelve hours the 

 branch would lose a dozen teaspoonfuls. 



But such an estimate was far from being exact. Guet- 



182. Discovery of the Transpiration of Plants. Muschenbroeck's experiment. 



tard managed better ; he conceived the idea of not separat- 

 ing the branch from the plant, but of inclosing it in a globe 

 of glass, terminating outwardly in a neck which was in- 

 serted into a flask. When all was hermetically sealed, the 

 moisture transpired, condensing itself on the sides of the 

 globe, fell drop by drop into the bottle situated beneath it, 

 and could be collected without the slightest loss, so that 

 nature was left to herself. 



Inclosed in this apparatus, a branch of a cornel-tree, 



