THE VEGETABLE KINGDOM. 407 



Thus there are vessels of plants, which though not so 

 thick as a hair, are yet more powerful than those of 

 animals that are thicker than the finger. 



After having made his experiments on the force of 

 ascent in the sap, Hales attempted to ascertain the 

 rapidity with which it moved. In order to arrive at this 

 point, he hollowed out a deep hole in the soil, laid bare a 

 small root of a tree, introduced it into a tube filled with 

 water, and plunged the tube into mercury. To his great 

 astonishment he very soon perceived that the metal rose 

 in the tube half an inch per minute. 



When we repeat this experiment in our amphitheatre, 

 as we do every year simply with a branch of a tree, we 

 often see the whole tube filled in half an hour with a 

 coloured liquid which had been placed in the lower vessel. 



The sap is formed and moves with such force in certain 

 plants, that it is not uncommon to be able to extract a 

 large quantity of it in a short space of time. The sugar- 

 maple (Acer saccharinum), scattered over the mountains 

 of Canada, produces a bucketful in a day. It is from this 

 tree that they get the greatest part of the sugar consumed 

 in the country where it grows. ^ 



For this purpose it is only necessary to pierce the tree 

 with a wimble ; the sap runs from it, and after being col- 

 lected is evaporated at the fire. The brown sugar con- 

 denses at the bottom of the evaporating pans. 



In the trojjical countries a tree yields a product not less 

 precious to man — a wine ready made. This is nothing else 



^The sap of the sugar-maple begins to rise in the month of Fehruary. In 



order to extract it they simply bore a hole in its trunk a few inches deep, and 



into this insert a tube which allows the iluid to drop into a pail. When 



fermented, it furnishes a light and agreeable wine, and when evaporated by a 



gentle heat, it yields a brown, viscid syrup, as sweet as treacle, which is converted 



into little sugar-loaves. Each tree produces yearly two to four pound.s. 



52 



