No. /.] OF MIXED MANURES. H 



this, though important to be made, should be tried cautiously, and on such a 

 scale as to secure the experimenter from any serious loss. 



In me above suggestions I have introduced nothing in regard to mixed ma- 

 nures — though where plants require for the supply of all their wants nine or 

 teii different ingredients, of which the soil they gi-ow in can perhaps yield in 

 sufficient quantity only three or four, it is obvious that the very best conse- 

 quences may follow from the employment of mixed manures. To this class 

 belong common night-soil, urine, animalised carbon, poudrette (night-soil mixed 

 with lime and gypsum), the poudre vrgetaiif (a mixture of soot and saltpetre), 

 the urate (now manufactured in London), and many others. 



The mode of preparing, and the special uses of these and other mixed ma- 

 nures, will be explained in the third part of these lectures, which will be devoted 

 to the consideration of the nature and uses, and to the theory of the action of 

 natural and artificial fertilizers. In the mean time it is desirable, in the first 

 place, to obtain results from which the special action of each, when used alone, 

 can be fairly deduced. 



That these experiments may have their full value, it is indispensable that a 

 measured portion of each field should be left without manure or aressing of any 

 kind, in order that a true idea may be formed of the exact effect of each sub- 

 stance employed. Experiments are valuable to the practical man if they mere- 

 ly show the superiority of one species of manure over another, but they are in- 

 sufficient to show how much each of them tends to increase the produce — or to 

 enable us to arrive at a satisfactory explanation of tlie mode in which they 

 severally act in promoting vegetation. 



Among other important experiments lately published, to which the above ob- 

 servation is apphcable, may be mentioned those of Mr. T. Waite of Doncaster. 

 The effects of nitrate of soda on his land were very striking, showing a remarkable 

 increase of produce over bone dust, rape-dust, or rotten fold-yard manure — but 

 he does not seem to have determined the produce of the same land during the 

 same season and vdLhmit inanure. We have, therefore, no term of comparison, 

 by means of which we can ascertain the absolute or even the exact comparative 

 effect of the different substances employed. 



It has been well observed by Sir Elumphry Davy, "that nothing is more 

 wanting in agriculture than experiments m which all the cir cum stances are mi- 

 nutely and scientifically detailed, and that this art will advance in proportion as 

 it becomes exact in its methods."* The above suggestions are submitted to 

 practical men in the hope that they may assist in introducing such exact meth- 

 ods into our agricultural operations, and at the same time promote the theoreti- 

 cal advancement of the most important art of life. 



Exact methods lead to theoretical discoveries, while these are no less certain- 

 ly followed by important practical improvements. 



No. ir. 



{See Lecture II., p. 37.) 



In illustration of the effect of sudden alternations of temperature on vegetable 

 substances, explained in a note subjoined to page 37, I quote with pleasure the 



the weight of 5 lbs. When perfectly ripe, it is said to be an excellent table potatoe, and to be 

 best in Ihe spring.— ^/6any Cultivator, for March, 1841. 

 * Agricultural Chemistry, Lecture L 



