1882.] 
Agricultural Possibilities . 
529 
magnesia is more abundantly present in the soil than lime, 
or the most important crops require it in a much less pro- 
portion. Neither, however, of these two suppositions is 
correct ; even in soils derived from the decomposition of do- 
lomite lime is found in a larger proportion than magnesia. 
And in not a few crops magnesia predominates over lime 
precisely in that part of the plant which is least likely to be 
returned to the soil. Thus in 1000 lbs. of the ashes of the 
grain of wheat, which in the ordinary course of things is 
sold, and ultimately finds its way into the sewers, there is 
found, according to Prof. Johnston, 120 lbs. of magnesia as 
against 28 of lime. But in the ash of the straw of wheat, 
which is very much more likely to be returned to the soil, 
there is only 39 lbs. of magnesia to 67 of lime. In the grain 
of barley, oats, rye, and maize, and also in beans and turnips, 
magnesia predominates. I do not therefore see how we can 
avoid the conclusion that the magnesia of arable lands must 
be more rapidly exhausted than the lime. General expe- 
rience, in England at least, has certainly not confirmed the 
value of gypsum except for certain specific crops, such as 
clover, peas, beans, &c. Grain-crops have not received any 
appreciable benefit from its use. 
The author fully recognises the low value of humus as a 
fertilising agent. Indeed, except as a means of rendering 
the soil more able to absorb and retain moisture, vapours, 
and gases, such as ammonia, and of supplying carbonic acid 
to effect the solution of carbonates of lime and magnesia 
and certain phosphates, few chemists will doubt M. Ville’s 
opinion that it is without any direCt utility. 
I may perhaps here be allowed to refer to a point in which 
the experience of gardeners, nurserymen, and florists is at 
variance with the teachings of agricultural chemistry. The 
former lay much greater weight upon the physical condition 
and the texture of the soil than do the latter. Thus the 
florists’ sheet-anchor is “ loam.” By this term he under- 
stands not the “ loam ” of the farmer, but simply the top 
spit of old pasture-lands, pared off and laid in a heap till the 
roots of the grass, &c., have rotted away. Now there needs 
no proof that the chemical composition of such “ loam ” 
must vary greatly, according to the geology of the district, 
the manures which may have been applied, &c. Yet I have 
never seen, in any treatise on floriculture, reference to these 
important distinctions. I cannot help thinking that if gar- 
deners were to pay greater attention to the chemical require- 
ments of their crops their results would be improved. 
The main point in M. Ville’s work is his most successful 
