IS THE REMEDY WORSE THAN THE DISEASE. 
553 
the perchloride of iron, which effectually precipitates organic 
matters. Dr. Letheby, however, in his report to the Com¬ 
missioners of Sewers of the City of London, states that there 
is an uncertainty in this proposed plan for deodorizing the 
river, and although, “ happily for us, there is evidently some 
condition wanted to make f this filthy river capable of gene¬ 
rating cholera, or of forming a soil fit for the germination of 
the seeds of that disorder when introduced into it,’ vet this 
is no argument for the neglect of sanitary precautions, or for 
disregarding every means for abating the noisome condition 
of the river. Nor is it a reason for temporising with the 
mischief, by resorting to any doubtful expedient that may 
merely serve as a disguise for the nuisance/ 5 Already, he 
adds, “ I have reported on this matter, and have directed 
your attention to the uncertainty of the proposed plan for 
deodorizing the river by means of perchloride of iron. But 
since then I have ascertained that the perchloride is highly 
charged with a compound of arsenic, which is exceedingly 
poisonous. A sample of the liquid furnished to me by the 
patentee, Mr. Dales, and described by him as the same as 
that used in the experimental inquiries for the Board of 
Works, has yielded from 296 to 297 grains of chloride of 
arsenic per gallon. If, therefore, the sewage of London were 
deodorized in the way proposed, there would be discharged 
daily into the Thames as much as 227 pounds of chloride of 
arsenic. I cannot tell you what would be the consequence 
of this, but it would be equivalent to the casting into the 
river about one hundred weight and a half of powdered 
arsenic daily. It is true that the poison would be diluted 
with a large quantity of water and with many millions of 
gallons of sewage, but a knowledge of this fact would afford 
no relief to our apprehension of danger, or to the anxiety that 
must be felt lest the accumulated effects of the poison might 
not, in the course of a very short time, be dangerous in the 
extreme/ 5 
En passant, it might be here observed, that in investigating 
suspected matters for arsenic by Marsh’s process, great 
care should be taken to ascertain that the sulphuric acid 
employed is not contaminated with that mineral substance, 
as much of this acid in the market is made from pyrites, in 
which arsenic exists often largely. Hence the advantage of 
effecting the decomposition of the suspected solution by means 
of electricity. 
