Injurious Manufactories . 29 
purposes for which it is used, it diffuses to a distance 
a very strong smell of vinegar, in which there is no dan- 
ger ; but when a solution of lead in this acid is evapo- 
rated, the vapours assume a sweetish character, and pro- 
duce in those who respire them constantly, all the effects 
peculiar to the emanations of lead itself. Happily these 
effects are confined to the people who work in the manu- 
factory, and are unfelt by those who dwell in the vi- 
cinity. 
The preparations of mercury and of lead, those of 
copper, antimony, and arsenic, and the processes of gild- 
ing on metals, are none of them without some danger to 
the persons who reside in those manufactories, and are 
concerned in the operations ; but their effects are bound- 
ed by the walls within which they are carried on, and 
are dangerous only to the persons concerned in the ma- 
nufactories. It is an object well worthy the attention of 
chemists, to investigate the means of preventing these 
injurious effects, and indeed many of the inconveniencies 
have already been prevented by the help of chimneys, 
which convey the vapours into the air out of the reach of 
respiration ; and at the present the whole attention of ad^ 
ministration ought to be confined to directing science to- 
ward the means of improvement of which these pro- 
cesses are susceptible with regard to health. 
The fabrication of Prussian blue, and the extraction of 
carbonate of ammonia by the distillation of animal sub- 
stances in the new manufactories of sal ammoniac, pro- 
duce a large quantity of fetid vapours or exhalations. 
These exhalations, it is true, are not injurious to health ; 
but as it is not sufficient to constitute a good neighbour, 
not to be a dangerous one merely, but not even to be a 
disagreeable one, they who undertake such manufac- 
tures, when they have to seek a situation for them, should 
prefer one remote from any dwelling-house. But when 
