CHEMIAL MANUFACTURES IN GLASGOW, ETC. 201 
of seven tons of coal for every ton of cast iron, three, or even 
two and a half tons will suffice. There is also a diminution 
of the quantity of lime stone necessary, and the produce of 
iron per week from the same furnace, is considerably increas- 
sed. It is said that neither in Staffordshire nor in Wales, is 
the hot blast attended with the same saving of fuel. Till of 
late years, no bar iron was made in Scotland, the smelters 
confining themselves to cast iron. About three years ago, 
Mr. Dixon commenced the manufacture of bar iron near St. 
Rollox, but, after some time, he abandoned the manufactory. 
It is now conducted on a grand scale by Mr. Wilson, at 
Dudyvon, and by Mr. Dixon, at Glasgow, and perhaps by 
other iron masters. The heat raised in the puddling furnace, 
is much greater than it was in Staffordshire, when Dr. Thom- 
son witnessed the process, there about twenty-five years ago. 
There is an interesting manufactory of steel near Holytown, 
not far from Airdrie, where the smelting and casting of steel 
may be seen ; the heat necessary for this purpose, is greater 
than for any other. It is curious that the clay in the neigh- 
borhood, answers perfectly for making crucibles for cast steel; 
but it does not answer so well as Stourbridge clay for making 
glasshouse pots. On analysing the two clays, it was found 
that the Garnkirk, contained much more alumina, and less 
silica than the Stourbridge ; showing that glass infusion acts 
much more powerfully on alumina than on silica. 
2. Another manufactory of importance, and which is in- 
debted to Glasgow for the state of perfection, which it has 
reached, is Sulphuric Acid. It was begun by Dr, Roebuck, 
at Preston-pans, about the year 1763, but it is not more than 
twenty years since his manufactory was abandoned. 
The Sulphuric acid works at St. Rollox, on the banks of 
the Monkland canal, were begun about forty-five years ago. 
They were at first upon a very small scale, though they are 
now, probably the largest of the kind in Europe. Dr. Roe- 
buck's method was to mix together sulphur and saltpetre, and 
after setting the mixture on fire, to introduce it into a leaden ves- 
sel or chamber, at the bottom of which there was a quantity 
