466 



the vegetative process by intermixture with the soil. The 

 oxide and sulphuret of iron, and the carbonate and sulphate 

 of lead, as well as the soluble salts of zinc, when present in 

 the proportion of about one per cent, of a dilute liquid 

 manure of human excrement, I have found unfriendly to the 

 health of blades of grass, which become brown in colour and 

 curled towards their points ; whilst there are no such ejOPects 

 when similarly treated with the alkaline salts, including those 

 of magnesia and lime. 



Burnett's fluid, in common with those of Ledoyen and 

 Ellerman, has double the density of water, and is free from 

 smell, which is a great advantage in the use of them. It is 

 sold wholesale at 5s. a gallon, and is said to contain 200 

 grains of the salt to each ounce of the liquid. 



During the sad prevalence of the late Irish fever, the 

 preparation of Ledoyen and Calvert was much commended 

 by high authorities, and apparently very successfully em- 

 ployed as a deodorising agent in the wards of the sick. The 

 soluble salts of lead are assuredly proved to decompose and 

 neutralize the prominent effluvia of decaying animal and 

 vegetable matters, so as to produce inodorous compounds with 

 them, or very nearly so. The resulting chemical action is 

 almost identical with that of zinc, but a preference has been 

 sought for this fluid, on the ground that the lead permanently 

 assumes an insoluble form, and that the nitrate of ammonia 

 is a more valuable fertilizer to the soil than the muriate. 

 This view is, therefore, founded on the assumption that had 

 the salt of lead, which is formed when mixed with animal 

 manures, been in an otherwise than insoluble state, a noxious 

 efiect to the crops might be expected from soils dressed with 

 this compost; but, as already observed, all the salts with 

 metalUc bases are more or less injurious to the vegetative pro- 

 cess, a union being formed by the eliminating power of the 

 vital functions of the plant, analogous to that which we find 



I 



