396 THE UNIVERSE. 



part of his life in a pair of scales, weighing and reweighing 

 himself every minute in the day, in order to ascertain how 

 much loss his body underwent by transpiration. 1 



Hales, without having the same perseverance, attempted 

 to ascertain what weight of water a sunflower lost daily by 

 its leaves. For this purpose 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 weighing this sunflower 

 daily his scales showed him that it lost, by the transpiration 

 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 sunflower, found that the former is to the latter 

 as 26 to 10, and that consequently, with equal surfaces, the 

 insensible transpiration of the sunflower is seventeen times 

 as great as our own. 



In some plants the phenomenon does not take place so 

 mysteriously ; their leaves transpire with surprising abun- 

 dance , water streams from all their pores. 



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

 house in the botanical garden at Amsterdam, distilled water 

 drop by drop from the extremities of its leaves in propor- 

 tion, so to speak, as it was watered. 



One might think there was some hyperbole in this, but 

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

 perimenter of Toulouse, have proved the thorough exact- 



1 Experiments show that on an average a man loses 2.2 Ibs. avoirdupois of wa- 

 tery vapor by means of his skin in twenty-four hours. 



