THE VEGETABLE KINGDOM. , 423 



ality has become celebrated, had the patience to pass a 

 great part of his Ufa in a pair of scales, weighing and re- 

 weighing himself every minute in the clay, in order to 

 ascertain how much loss his body underwent by trans- 

 piration. ^ 



Hales, without having the same perseverance, attempted 

 to ascertain what weight of water a sun-flower lost daily 

 by its leaves. For this pi;rpose he put one of these plants 

 into a pot, the upper surface of which, hermetically closed 

 with a plate of lead, only presented one small neck through 

 which it could be watered. By Aveighing this sun-flower 

 daily his scales showed him that it lost, by the transpira- 

 tion of its leaves only, twenty ounces of water in the 

 twenty-four hours. 



The experimenter having subsequently calculated the 

 difference in extent between the skin of a man and the 

 leaves of a sun-flower, found that the former is to the 

 latter as 26 to 10, and that consequently, with equal sur- 

 faces, the insensible transpiration of the sun-flower is 

 seventeen times as great as our oAvn. 



In some plants the phenomenon does not take place so 

 mysteriously ; their leaves transpire Avith surprising abund- 

 ance; AA^ater streams from all their pores. 



Ruysch states that an Arum, Avhich he kept in a green- 

 house in the botanical garden at Amsterdam, distilled 

 Avater drop hj drop from the extremities of its leaves in 

 proportion, so to speak, as it was Avatered. 



One might think there Avas some hyperljole in this, but 

 recent and curious observations, which Ave owe to an ex- 

 perimenter of Toulouse, have proved the thorough exact- 

 ness of the fact put forAvard by the great Dutch anatomist. 



'Experiments show that on an average a man loses a kilogramme (2 lbs. 3 oz. 



4^ drs. avoirdupois) of watery vapour by means of his skin in twenty-four hours. 



64 



