226 ANNUAL OF SCIENTIFIC DISCOVERY. 







was passing before him. The carbonate of ammonia produced in the 

 layers of dung, volatilized by the action of the sun, became decomposed 

 in its passage through the gypsum, forming carbonate of lime and sul- 

 phate of ammonia. 



Several experiments proved to M. Mene, that the results were ob- 

 tained by these means, and, having watered some flower-pots contain- 

 ing dung, in which some grass-seed was sown, with sulphuric acid, 

 sulphate of potassa, hydrochloric acid, chloride of manganese, nitric 

 acid, phosphate of soda, acetic acid, sulphate of magnesia, sulphate of 

 iron, and nitrate of soda, he found the grass developed rapidly, and that 

 fixed ammoniacal salts ran off through the bottom of the flower-pots in 

 which the experiments were made. Gypsum, therefore", has not of 

 itself any fertilizing quality ; it only acquires a fertilizing property 

 when it comes in contact with those ammoniacal salts which it is 

 capable of decomposing. It would appear from this that sulphate of 

 lime might be replaced by any other salt possessing the property of 

 retaining ammonia in a fixed state at ordinary temperatures. 



MINERAL THEORY OF BARON LIEBEG IN RELATION TO AGRICULTURE. 



AT the British Association Messrs. Lawes and Gilbert presented the 

 results of an extensive series of experiments on the growth of the prin- 

 cipal crops entering into a rotation, as well as on the chemistry of 

 plants in relation to the soil and atmosphere ; all of which experiments 

 they consider conclusive against the "Mineral Theory' 1 ' of Liebeg, 

 which asserts that the crops of a farm rise or fall according to the 

 supply within the soil of the mineral constituents indicated by the 

 analysis of the ashes of the plants. The results selected in justification 

 and illustration of their views, were those of the field experiments on 

 wheat, grown continuously, on a previously exhausted soil, for the last 

 eight years, and in each season, by means of many chemical ma- 

 nures, by the side always of one or more plots unmanured, and one 

 manured continuously by farm-yard manure. From this it appeared 

 that mineral manures had scarcely increased the produce at all when 

 used alone, whilst the effects of ammoniacal salts were very marked, 

 even when repeated year after year on the same space of ground from 

 which the entire crop, corn and straw, had been removed. Indeed, 

 io this way, a produce had been attained, even in the sixth and seventh 

 succeeding years of the experiment, exceeding by nearly two thirds 

 that from the unmanured plot. It was then shown that the mineral 

 constituents of the soil continued to be in excess, relatively to the 

 nitrogen available for them from natural sources. The history of sev- 

 eral plots was then traced down to the last harvest, (1850,) and it 

 was agreed that the statement assailed by Liebig, viz., that ammonia 

 was specially adapted as a manure for wheat, was fully borne out 

 when speaking of agriculture as generally practised in Great Britain. 

 In other words, that in practice it was the defect of nitrogen rather 

 than of the mineral constituents that fixed the limit to our produce of 

 corn. The authors next called attention to the fact of the exhalation 

 of nitrogen by growing plants, as proved by the experiments of Do 



