W. F. Cooper and W. A. B. Walling 171 



important properties for the purpose. It is extremely fine, and experi- 

 ments carried out in the laboratory suggest that it could be blown into 

 the wool as a spray. Oils are readily absorbed by precipitated chalk, 

 consequently this is a very useful method of diluting them. Non-acid 

 solids in powder form can be mixed with it. Chalk is quite neutral 

 and in no way affects the wool. It would not, like lime, combine with 

 soap, so that the treated wools would scour well and dye evenly. 

 Precipitated chalk is obtained in large quantities as a waste product 

 in the process of water softening and costs little more than freightage. 



In Australia, water is not altogether desirable as a vehicle for 

 treating sheep ; it is not always very plentiful and it sometimes causes 

 damage to the wool, which is usually long just at the time when it is 

 necessary to apply the remedy. There is also the difficulty in wetting 

 the fleece with an aqueous solution, but this is overcome to a con- 

 siderable extent by the addition of an emulsion. 



The use of an active chemical dissolved in an inert oil which is then 

 emulsified by the addition of soap or some other emulsifying agent has 

 certain advantages. It affords a means of applying chemicals which 

 are insoluble in water. The emulsified liquid would also possess a 

 high wetting power, a most desirable property where a greasy fleece 

 is concerned. 



Many substances are efficient insecticides in the form of vapour, 

 and as the larvae breathe through spiracles, the method appeared to be 

 worthy of trial. The treatment of lung-worm infection in sheep by 

 inhalation of suitable vapours has been practised with some success 

 in S. America and it would appear that some modification of this process 

 might also be applied to the treatment of the fly pest, though the numbers 

 of sheep to be treated might render it impracticable. A few experiments 

 were carried out with the object of observing the effect of various vapours 

 on larvae. 



In determining the susceptibility of the larvae to various chemicals, 

 therefore, our experiments fall under three heads : 



(a) Those with a powder basis. 



(b) Those with emulsions. 



(c) Those with vapours. 



It is obviously impossible in this country to carry out experiments 

 on living sheep with the very large number of chemicals involved. It 

 was, however, desirable that our laboratory experiments should simulate 

 natural conditions so far as possible, and, for this reason, our earlier 

 experiments were carried out on pieces of fresh sheep-skin. The skin 



