ARSENIC IN THE SOIL AND PLANTS. 
413 
for November, 1859), states, from his experiments, that he 
doubts that plants are capable of absorbing arsenic at all; 
whereas Dr. Davy not only detected the presence of that sub¬ 
stance in plants which had been watered with a solution of 
arsenious acid, but in several instances determined the amount 
which had been taken up or absorbed. Again, Mr. Ogston, 
of London, in the Pharmaceutical Journal for March, I860, 
states that in plants which he had similarly treated, he found 
arsenic only in the portion of the stem close to the roots, but 
that in no case could he discover it in the leaves or in the 
stem at more than five inches from the ground. 
Dr. Davy, on the other hand, detected it in the leaves, and 
in every portion which he examined of the different plants 
which had been watered with a solution of arsenious acid ; 
and he accounted for Mr. Ogston’s failing to detect it in the 
leaves, where probably it existed in a smaller quantity, by his 
using Marsh's method, which as Professor Odling has re¬ 
cently shown, is not applicable for the detection of minute 
quantities of arsenic where much organic matter is present. 
Again, Mr. Sibson, of the Royal Agricultural College, 
Cirencester, asserts in the Gardener's Chronicle for September, 
1859, that the occurrence of arsenic in super-phosphates is 
rare, and its quantity when present is generally exceedingly 
small; and he gives the results of some experiments which 
would appear to indicate the same. 
Dr. Davy’s experience, however, is diametrically opposed 
to the results of Mr. Sibson, for he found arsenic in almost 
every sample of superphosphate which he examined, as well 
as in different other artificial manures, in the preparation of 
which sulphuric acid had been employed; and, as this acid, 
which is used in large quantities, frequently contains, he finds, 
several pounds weight of arsenic in the ton of acid, the amount 
of that substance in superphosphate and other artificial 
manures, cannot be so very inconsiderable as Mr. Sibson 
would have us believe. Dr. Davy also noticed some in¬ 
teresting experiments which Mr. Horsley, of Cheltenham, 
had made and communicated to him, on the same subject of 
the absorption of arsenic by vegetables, which confirmed, in 
the most satisfactory manner, his former statements, and 
showed that plants, under different circumstances, were 
capable of taking up that substance; from which he (Mr. 
Horsley) has come to the conclusion that arsenic applied to 
the roots of plants, under any form, is taken up by them, 
some, perhaps, absorbing it more readily than others. Finally, 
Dr. Davy stated that he had succeeded in detecting the pre¬ 
sence of arsenic in different crops, as for example, in turnips, 
