CHEMISTRY. 293 



view of all. They have learnt that the approved artificial manures are not 

 mere stimulants, but agents of fertility which, when properly applied, may be 

 depended upon with certainty to produce a crop. The principles on which 

 the growth of corn depends are better understood. The repetition of corn 

 crops on the same soil can no longer be considered as necessarily faulty in 

 principle, and to be unconditionally condemned. It is rather a question of 

 expediency, to be decided by the cost of manure and of produce. 



These lessons the English farmers have learnt from Mr. Lawes. They have 

 accepted them with becoming gratitude. They are practising them with 

 increasing confidence, day by day, to their great and proved advantage. 

 The department of agricultural chemistry is now attracting to itself the atten- 

 tion of able chemists in all countries ; and the contributions to knowledge 

 resulting from the various investigations have, during the last few years, been 

 very considerable. To attempt anything like an account of these results in 

 this place is obviously out of the question, and we content ourselves with little 

 more than an enumeration of the principal and most interesting investigations. 



In this country, Mr. Lawes has continued his experiments on the laws 

 concerned in the feeding and fattening of animals, taking, for the objects of 

 his trial, pigs and sheep. The number of animals experimented upon, the 

 intelligence and care brought to bear upon every detail of the experiments, 

 and the very considerable expenditure which has evidently accompanied 

 them, place these investigations far in advance of any of a similar kind that 

 have been undertaken elsewhere. Although the results are of a practical 

 character, the experiments of Mr. Lawes must not be classed with the very 

 numerous trials on the feeding of animals that are to be found dispersed 

 through agricultural publications, and which are merely practical, being under- 

 taken without reference to general principles. The results of Mr. Lawes' 

 inquiries are too numerous to be stated here ; but they seem to point out that 

 a just balance of 'the different constituents of food is of more importance in the 

 feeding and fattening of cattle than a predominance of any one ; that neither 

 the albuminous nor farinaceous elements of food have an exclusive value for 

 the purposes to which they are applied ; and that the classes of vegetables 

 which are peculiar in containing a high proportion of nitrogenous matter, are 

 not necessarily, from that circumstance, the most adapted in practice to 

 produce that part of the animal body (muscle) which most resembles them ha 

 composition. According to Mr. Lawes, therefore, the valuation of foods in 

 relation to their contents in nitrogen is attended with much fallacy. 



Amongst other papers, Dr. Ycelcker, of Cirencester College, has published 

 an account of experiments made with a view of ascertaining the cause of the 

 fertility produced by burnt clay when used as manure. He has arrived at 

 the opinion that the effects are partly mechanical, but principally due to the 

 liberation of potash from silicates of that alkali existing in the soil, but only 

 slowly available until released by torrefaction. 



Mr. Way has published two further papers on the important subject of the 

 absorption of manure by soils, in continuation of his first research on this 

 subject, which was published in 1850. Mr. Way attributes the power 

 possessed by soils to remove various alkaline bodies (as potash, ammonia, &c.), 



