24 Injurious Manufactories . 
of the manufacturer, and gradually extinguish both his 
courage and his powers. 
It is an object of primary necessity therefore to the 
prosperity of the arts, that lines should be drawn, so as 
no longer to leave any tiling at the arbitrary will of the 
magistrate ; to point out to the manufacturer the circle in 
which he may exert his industry with freedom and secu- 
rity, and to assure the neighbouring proprietor that he 
has nothing to fear for his health, or for the produce of 
his fields. 
To arrive at the solution of this important problem, it 
appeared to us indispensable, that|we should take a view 
of each of the arts, against which the most clamour has 
been raised. 
With this view we shall divide them into two classes. 
The first will comprise all those, the processes of which 
allow aeriform emanations to escape from them into the 
atmosphere, either in consequence of putrefaction or fer- 
mentation, which may be deemed nuisances from their 
smell, or dangerous from their e Herts. 
The second class will include all those, in which the 
artist, operating by the aid of fire, developes and evolves 
in air or vapour various principles, which are more or 
less disagreeable to respire, and reputed more or less in- 
jurious to health. 
In the first class we may advert to the steeping of flax 
and hemp, the making of catgut, slaughter-houses, 
starch-manufactories, tanneries, breweries, &c. 
In the second, the distillation of acids, of spirits, and 
of animal substances ; gilding on metals, preparations of 
lead, copper, and mercury, &c. 
The arts of the first class, considered in relation to 
the health of the public, merit particular attention, be- 
cause the emanations that proceed from fermentation or 
putrefaction are really injurious to health in some cases, 
