236 Dr THOMSON'S Experiments on the 



consisted of a mixture of silica, lime, phosphate of lime, and 

 magnesia *. 



The Galactodendron utile grows abundantly in the mountains 

 situated on the north-west part of Venezuela, in South America, 

 at a height, according to HUMBOLDT, of nearly 10,000 feet above 

 the level of the sea, and consequently in a climate that cannot 

 differ much from our own. The tree, from Mr LOCKART'S ac- 

 count, is a very large one, with leaves similar to those of the fig. 



The juice of this tree, obtained by incision, is known by the 

 name of the milk of the cow-tree. In the state in which I re- 

 ceived it, it was a white opaque liquid, of the consistence of 

 cream. When thrown upon a filter, a small quantity of a red- 

 dish-brown transparent liquid passed through, leaving a great 

 quantity of white solid matter on the filter, the surface of which, 

 as it dried, assumed a reddish-brown colour. The filter itself 

 became gradually tinged of the same colour. It was found im- 

 possible to wash this solid matter. It attached itself to the fil- 

 ter, and rendered it quite impervious to water. 



Another portion of the cow-tree milk was left for six weeks 

 in a state of rest in a tall cylindrical glass. No deposite took 

 place ; the milk remained unaltered, excepting that its surface, 

 where in contact with the air, assumed a reddish-brown colour. 

 But after four months, the white matter had separated, and left 

 a little brownish liquid at the bottom of the dish. 



It had a sour smell, not the same with that of vinegar, but 

 peculiar. Different individuals formed different opinions re- 

 specting this smell : some considering it as offensive, others as 

 rather agreeable. The milk reddened vegetable blues. It had 

 a very slightly acid taste, but in other respects bore considerable 

 resemblance to the taste of cream. 



Its specific gravity was found to be 1.01 42. 



* See an abstract of their experiments in the Ann. de Chim. et de Phys. xxiii. 219. 



