136 TlMEHRI. 
ledge of the importance of gypsum as a fertiliser, has 
recently been contributed by WARINGTON, perhaps the 
foremost amongst English chemists in researches into the 
chemical minutiae of agriculture. In a former paper* 
I have drawn attention to the fa6l that ammoni- 
acal salts, and other nitrogenous matters, become 
oxidised to nitric acid (or nitrates) in the soil, and 
that it is considered that this change is necessary 
before the nitrogen becomes assimilable by plants. 
The required change is brought about by a specific 
organism — a ba6terium — discovered in 1877 by SCHLOE- 
SING and MUNTZ. WARINGTON has ascertained that 
nitrification is greatly aided by the presence of gypsum. 
Experimenting with diluted urine, he found that whereas 
water mixed with 12 to 15 per cent, of urine was practi- 
cally unnitrifiable, (although weaker solutions were not) 
yet when gypsum was added, nitrification occurred sooner 
or later even when the proportion of urine was 
increased to 50 per cent. It appears from Waring- 
TON'S experiments that nitrification can not pro- 
ceed in the presence of a certain small proportion 
of alkali, and as urine by decomposition developes 
ammonium carbonate, which is alkaline, the reason of 
the non-nitrification of the stronger mixtures is evident. 
By the addition of gypsum, however, the ammonium 
carbonate is destroyed, insoluble calcium carbonate and 
ammonium sulphate being formed, and as the alkalinity is 
thus removed, the nitrification proceeds. Other organic 
nitrogenous matters also become alkaline by decom- 
position, from the formation of ammoniacal compounds, 
* Soluble vs. Insoluble Manures, Timehri, iii., 331. 
