133 



mucilaginous juice of the common cactus (Opuntia Englemanni) for 

 this purpose. To obtain this, the cactus leaves or stems are cut or 

 broken up into pieces, thrown into a barrel, and covered with water, 

 after which they are allowed to soak for three or four days. The liquid 

 portion is then drawn off, and i> ready for use without further prepar- 

 ation. Tents which I saw that had been prepared with this substance 

 were to all appearances as air-tight and pliable as when prepared in any 

 other manner.' 



For the oiling, Mr. Lounsbury recommends a mixture of four parts 

 boiled linseed oil to one part turpentine. The cloth should be first well 

 wetted with water, and the mixture spread lightly over the surface with 

 a brush. A thin coating is found to be sufficient. Mr. Lounsbury has 

 since informed me that he now uses, with completely satisfactory results, 

 tents made of cloth merely >hrunk in water, without any subsequent 

 oiling. Such tents are, of course much lighter and more easy to mani- 

 pulate. 



Mr. (Joquillet gives the annexed table, showing the quantities of 

 chemical- required for different sized trees. 



Height of 



Diameter of 



Water 



Sulphuric 



Potassium 



trf 3. 



tree top- 



Acid. 



Cyanide. 



Feet. 



Feet. 



Fluid ozs. 



Fluid ozs. 



Ozs. 



6 



4 



% 



l A 



l A 



8 



6 



2 



1 



1 



10 



8 



4* 



2* 



2X 



12 



10 



8 



4 



4 



12 



14 



16 



8 



8 



14 



10 



10 



5 



5 



14 



14 



19 



9y 2 



9# 



16 



12 



16 



8 



8 



16 



16 



29 



14>> 



14# 



18 



14 



26 



13 



13 



20 



16 



36 



18 



18 



22 



18 



52 



26 



26 



24 



20 



66 



33 



33 



Mr. Lounsbury, after practical experience at the Cape, publishes 

 the following figures, from which it appears that he found smaller 

 quantities sufficient. This is, doubtless, due to difference in purity of 

 the chemicals. Mr. Lounsbury was working with cyanide of 98 to 100 

 per cent, purity, while Mr. Coquillet was using cyanide of only 33 to 

 58 per cent. It is therefore important to know the exact amount of 

 pure potassium cyanide in the particular brand employed. 



