COPPER. 185 
that the proprietors employ more than 1000 workmen ; 
and that they ship, from the adjacent port of Amlwch, 
upwards of 20,000 tons of copper, annually. 
There is at Ecton, in Staffordshire, a copper mine 
which is now worked at the depth of 1446 feet below 
the surface of the ground. This is the deepest mine in 
England. 
The uses of copper are numerous and important. 
When rolled into sheets, betwixt large iron cylinders, it 
is employed for the covering of houses, sheathing the bot- 
toms of ships, and other purposes. As a covering for 
houses, copper is lighter than slate, but whether it be 
more durable has not been yet ascertained. The cop- 
pering of ships tends to facilitate their progress through 
the water, by presenting a smoother surface than that of 
wood, and not permitting shell animals to fasten to it as 
they do to wood. It likewise preserves the bottoms of 
the ships from being punctured by marine worms; and 
consequently secures to them a longer duration than they 
would otherwise have. Plates, or flat pieces of copper,' 
are used by artists for engraving pictures upon, either 
by cutting them with a sharp steel instrument, or cor- 
roding them with aqua fortis (206 ) in lines drawn by a 
needle through a thin coat of wax spread upon their 
surface. 
Copper is manufactured into various kinds of cook- 
ing utensils. Great care, however, ought to be taken 
that acid liquors, or even water intended for drinking, 
or to be mixed with food, be not suffered to stand long 
in such vessels, otherwise they will dissolve so much of 
the metal as to give them disagreeable and even poison- 
ous qualities. Yet, it is remarkable that, while acid 
liquors are kept boiling, they do not seem to dissolve 
any of the metal. Hence it is that confectioners, by 
skilful management, prepare the most acid syrups in 
copper vessels, without their receiving any unpleasant 
taste or injurious quality from the metal. All vessels 
formed of this metal which are employed in cookery, 
