202 SECONDARY PRODUCTS. 



produced in gas-works to be a valuable substitute for those manures, by the 

 application of which it is intended to supply the soil with nitrogen. 



It would be out of place to make any remarks upon the elements absorbed 

 from the earth by different plants, even if I had studied the subject sufficiently 

 to give my opinions to the world : we all know, however, that carbonic acid, 

 water and ammonia contain the elements which support both animal and 

 vegetable life, and that it is the object of the agriculturist, when he manures 

 his land, to supply the deficiency of any of these elements, from the want of 

 which his crops would fail. 



One of the most valuable manures is urine, and its excellence depends 

 almost entirely upon the ammoniacal salts which it holds in solution, and the 

 quantity of nitrogen it affords for the development of the seeds or roots of 

 those plants to which it is applied. The relative value of urine as manure 

 depends upon the quantity of nitrogen the different kinds yield. Thus human 

 urine is the most esteemed, and that of horned animals the least. 



According to Professor Liebig, 547 pounds of human excrement contain 

 16'41 pounds of nitrogen; a quantity sufficient to yield the nitrogen of 800 

 pounds of wheat, rye, oats, or of 900 pounds of barley. How much more, 

 then, will be supplied from an equal weight of ammoniacal liquor ! 



Mr. J. Watson, the manager of the Gas-works at Kirriemuir, has favoured 

 rne with the following facts : 



" The ammoniacal liquor on the surface of the tar-well has been found a very great 

 improvement as a manure for the raising crops of grass in this quarter, by being sprinkled 

 on the field in the same way as water is put on public streets in large towns, to keep 

 down dust in dry weather. I have myself seen an experiment of this tried, and can say 

 that part of a field of grass sprinkled in this way (after first cutting) was far superior to 

 any other part of the field receiving manure of any other kind, and that the part so 

 sprinkled or showered over was ready to be cut down a second time in the course of be- 

 tween fourteen days and three weeks ; whereas the other part of the field cut at the same 

 time, was only beginning to spring or rise from the roots in that time : it has to be mixed 

 up before use with four parts of common water. In particular, the said experiment of 

 the gas-water has been used by David Nairn, Esq., Doumkilba, near Meigle, in this 

 neighbourhood, with success ; and I am informed that he has purchased and taken a 

 lease of the ammoniacal liquor from different gas companies in this country." 



The statement of this fact will be more acceptable than the mere notice of 

 theoretical writers upon this subject, although much weight may be given to 



