Steam Engine, 
nearly as perfect as by the exhaustion of the air-pump. The 
whole of the steam and heat is usefully employed ; and the 
contrivance appears scarcely to admit of improvement. 
Such is the history of this valuable invention, which we 
have extracted from Dr. Black and Professor Robison’s 
testimonials, who were privy to Mr. Watt’s discovery ; 
as well as from some early letters of his own to confiden- 
tial friends, to which we have had access. 
We have entered thus minutely into the subject, from 
a desire to do that justice which is due to Mr. Watt, by 
showing that this great improvement was not the effect of 
accident, or of casual observation, but the result of deep > 
reflection, of great ingenuity, and much philosophical in- 
vestigation. 
It did not, at the early period wc have been speaking of, 
escape him, that great benefit might be derived from the 
direct application of the power of steam to driving 
mills, instead of using it to raise water to act on a wdieel, 
as had heretofore been done ; and with this view, he in- 
vented and executed the model Qf a steam wheel, for giving 
a circular motion to an axis. 
His occupations in the business of a civil engineer 
w^hich he had now taken up, perhaps also the indifferent 
state of his health, his want of funds, and his apprehension 
of the prejudices and opposition he might have to encoun- 
ter, prevented his applying for a patent for the invention 
we have described, until the year 1769. He had, we be- 
lieve, previous to, or about that time, erected an engine 
for his friend Dr. Roebuck of Kinneil, near Borrows- 
tounness, which, upon a large scale confirmed his expec- 
tations ; the proportionate saving of fuel being from two 
thirds to three fourths of that of engines on Newcomen’s 
construction. Dr. Roebuck, whose spirit for enterprise 
and improvement in the arts is well known, foresaw all 
the advantages likely to result from this invention, and be- 
