333 DR. K. ANGUS SMITH ON THE PRODUCTION 



intended for this country, the hind of great cities. This 

 plan for the disinfection of districts is intended chiefly to 

 apply to other countries. I may, however, be allowed to 

 give one illastration from this country. Mr. McDougall 

 has used sewage over one hundred acres of larid ; sheep 

 and cattle have fed on it without any case of disease. The 

 growth of vegetation was great, the moisture was constant ; 

 there was also the constant presence of decomposed matter, 

 but there was no disease. There was, on the contrary, a 

 large production of healthy vegetable and animal life. 

 This experiment suggests many questions, but I do not 

 intend to enter on any except so far as to show it as a 

 proof that putrefactive decomposition may be arrested 

 without any fear of destroying the life of plants, and that 

 rich water meadows may be used for feeding cattle without 

 fear of rot, even if treated with sewage. The disinfectant 

 used was crude carbolic acid with lime water.* The arrest 

 of decomposition was thus caused by a process which at 

 the same time diminished the acidity. I think the amount 

 required will be small enough to render the process pos- 

 sible over large districts. At the same time also I expect 

 that the idea will lead to other and perhaps even to cheaper 

 modes of producing a like result. As it is to be hoped 

 that an opportunity of using it will occurj it is well not 

 to attempt to speak of details. 



I may add also at the same time that the extinction of 

 insects obnoxious to a country, — gnats, mosquitoes, and 

 those dreadful enemies of cattle the zimb and the tsetse, — • 

 will probably follow the destruction of the obnoxious de- 

 compositions in the soil. Nor do I suppose that only 

 one disinfectant will do the work, although the one I 



* The value of carbolic acid has elsewhere been shewn by Mr, Mc Dongall 

 and myself; the preparation here used was that patented by Mr. McDou- 

 gall in 1859. He will be able soon to make public many other experiments 

 relating to rot and the destruction of insects. 



