662 
ARSENIC IN ARTIFICIAL MANURES. 
I examined, its specific gravity being only about 1 780 
whereas the usual strength of the acid is 1*845. Dr. Owen 
Rees found 13*5 grains of arsenious acid in 12 fluid ounces 
of commercial sulphuric acid; and Mr. Watson, in the 
London Medical Gazette , states that the smallest quantity of 
arsenious acid which he detected in the same amount of com¬ 
mercial acid was 21*3 grains. There is therefore every reason 
to suppose that the acid usually employed for agricultural 
purposes contains a far greater quantity of arsenic than the 
sample I examined; and as the proportion of sulphuric acid 
used in making these artificial manures is very large (thus, 
for example, in the manufacture of superphosphates, the 
most valuable manure of this class, about one ton of acid is 
used for every two tons of bones employed), the quantity 
of arsenic present in such manures must be considerable. 
These facts appear to me to have some important bear¬ 
ings, for though the quantity of arsenic which occurs in 
such manures is not large when compared with their other 
constituents, and the proportion of that substance which is 
thus added to the soil must be small, still plants may, during 
their growth, as in the case of the alkaline and earthy salts, 
take up a considerable quantity of this substance, though its 
proportion in the soil may be but very small. Further, as 
arsenic is well known to be an accumulative poison, by the 
continued use of vegetables containing even a minute propor¬ 
tion of arsenic that substance may collect in the system till 
its amount may axercise an injurious effect on the health of 
man and animals. 
As connected with this subject, I may observe that I was 
informed of a curious fact—that sheep did not appear to like 
Mr. Rathbone’s turnips which were grown with superphos¬ 
phate, so well as those where the ordinary farm-yard manure 
had been employed, and that they could not be made to eat 
enough of the former turnips to fatten them properly. If 
this was really the case, it w r ould appear to favour in some 
degree my views as to the probable unwholesomeness of vege¬ 
tables grown with manures containing, even in small quan¬ 
tities, so deadly a poison as arsenic, which my experiments 
have shown that plants are capable of taking up from such 
manures. 
Finally, these investigations appear to have a medico-legal 
bearing; for in cases of suspected poisoning by arsenic, 
where the evidence may chiefly depend on the detection of a 
small quantity of that substance in the liver and other 
viscera, as is sometimes the case, my experiments would tend 
to throw much doubt and uncertainty on such cases, because 
