BULLETIN OF THE BUSSEY INSTITUTION. 305 
house would have included that of the experimental plants, and 
the gardener would have had only the extra trouble of watering 
the plants with the chemical solutions. 
I am aware that Ville has predicted conclusions* very unlike 
those at which I have arrived. I can only say that I have hitherto 
been unable to find anything in Ville’s published experiments 
which leads me in the least degree to change my opinion of the assay 
by sand culture. I deem the assay incompetent to give sharp, 
well-defined results, as between one loam and another; and I am 
convinced that the results it does yield, in respect to loams are 
in no wise commensurate with the time, labor, and trouble they 
cost. 
But though of little or no practical use for assaying cultivable 
earths, the process is valuable as a method of scientific research 
for testing sands, and some coarsely powdered rocks, or the like 
‘‘inert” materials; and as a means of detecting small or even 
minute quantities of available nitrogen. Indeed it has no small 
merit as a qualitative test to be used in certain cases. I have 
shown already in papers printed in 1874 and 18777 that a just 
conception of the value of anthracite ashes, regarded as a source 
of plant-food, may be gained in this way; that some part of the 
nitrogen { in peat, loam, and roasted leathers is immediately 
available for plants, and that even coal slack may often contain 
enough ammonia to promote the growth of plants. Calcined loam 
and mixtures of calcined loam and inert sand afford admirable 
soils in which to test the question whether a given chemical com- 
pound containing nitrogen (an amid, for example) is capable of 
supplying nitrogenous food to plants. Probably the best way of 
testing such a substance, in case it is soluble in water, would be to 
put occasionally small-weighed quantities of it upon the soil and 
to use rain-water all the while for watering. So, too, there could 
hardly be a better way of illustrating the economy of the carni- 
verous plants which have lately attracted so much attention than 
to transfer them to a calcined garden-soil and feed them there, for 
a considerable interval of time, with meat and egg, and insects, 
in contrast with other kinds of plant-food. 
The following tables show the comparative value of several 
common sands : — 
* ‘¢ Chemical News,” 1874, 30. 288. 
+ Bussey Bulletin, 1.50; 2. 159. 
t Ibid. 1. 62, 252, 398; 2. 58, 72, 280. 
