W A 
lower, in order to make the vacuum complete. Earl y in 
1765, the fortunate thought occurred to him of accomplish¬ 
ing this, by condensing the steam in a separate vessel, ex¬ 
hausted of air, and kept cool by injection, between which 
and the cylinder a communication was to be opened every 
time steam was to be condensed, while the cylinder itself was 
to be kept constantly hot. No sooner had this occurred to 
him, than the means of effecting it presented themselves in 
rapid succession. A model was constructed, and the ex¬ 
periments made with it placed the correctness of the theory, 
and the advantages of the invention, beyond the reach of 
doubt. 
He also, at this time, made experiments upon the capaci¬ 
ties of different bodies for heat, and upon the heats at which 
water boils under various pressures; from which he ascer¬ 
tained, that where the heats proceeded in an arithmetical, 
the elasticities proceeded in a geometrical ratio, the curve of 
which he laid down. These he repeated some years after 
with more accuracy. 
From this period (the early part of 1765), his mind be¬ 
came very much engaged in contriving the machinery for 
executing his improvement upon a large scale; but the want 
of funds prevented his attempting it, until he was induced to 
address himself to Dr. Roebuck, who had a short time 
before completed his establishment of the Carron Iron-works, 
and who, in addition to his known qualities of ingenuity 
and enterprise, was considered to be possessed of ample 
means of introducing the invention to the public. He agreed 
to enter into the plan, upon having the proceeds of two- 
thirds of the invention assigned to him; and an engine upon a 
large scale was then constructed by Mr. Watt, at Kinneil, near 
Borrowstounness, where the Doctor then resided; the trials 
made with which gave satisfaction. But the introduction of 
the invention to the public was retarded, on the one hand, 
by the pecuniary difficulties in which the Doctor became in¬ 
volved, by the failure of several of his multifarious under¬ 
takings ; and on the other day, by the employment, which 
the rising reputation of Mr. Watt, for knowledge and skill in 
the line of a civil engineer, procured him. 
He was employed, in 1767, to make a survey for a canal 
of junction between the rivers Forth and Clyde, by what was 
called the Lomond passage, and attended Parliament on the 
part of the subscribers, where the bill was lost. An offer was 
then made to him of undertaking the survey and estimate of 
an intended canal from the Monkland collieries to Glasgow ; 
and these proving satisfactory, the superintendence of the 
execution was confided to him. The last and greatest work 
upon which he was employed was the survey and estimate 
Of the line of a canal between Fort-William and Inverness, 
since executed by Mr. Telford, upon a larger scale than was 
at that time proposed, under the name of the Caledonian 
Canal. 
Whilst engaged upon this survey, in the latter part of the 
year 1773, Mr. Watt received the account of the death of 
his affectionate wife, leaving him a daughter and a son. He 
had secured his title to his Improvements for saving Steam 
and Fuel in Fire Engines, by patent, in the year 1769; but 
all hopes of carrying them into effect, by the assistance of 
Dr. Roebuck, being at an end, he had induced that gentle¬ 
man to agree, for certain considerations, to transfer his share 
of the patent to Mr. Boulton, of Soho, near Birmingham—a 
gentleman equally distinguished by his knowledge of the 
arts, and his enterprising spirit, who had some years before 
established his manufactory upon a scale as unrivalled for 
extent and elegance, as for the variety and perfection of the 
processes carried on. 
In conjunction with him an application was made to Par¬ 
liament for an extension of the term of the patent, and an act 
prolonging it for twenty-five years was obtained in the year 
1775, when the business of making steam-engines was com¬ 
menced by the firm of Boulton and Watt. 
Mr. Watt now married for his second wife Miss Macgrigor, 
the daughter of an old friend, at Glasgow, and devoted him- 
Vol. XXIV. No. 1658. 
T T. 585 
self to the improvement of the details of the engine with a 
degree of application and exertion not to be expected from 
his delicate and infirm state of health ; and he found in his 
partner a zealous and able coadjutor. 
Some engines for pumping water were soon made upon a 
large scale, and the savings in fuel were demonstrated by 
repeated comparative trials to amount to three-fourths of the 
quantity consumed by those of the best construction before 
in use. A deputation from the mining interest of Cornwall 
was sent to ascertain the fact, and their report led to the 
introduction of the improved engines into that county, to 
which they have proved of such vast utility. 
The immediate application of the powers of steam to 
giving a rotatory motion to mills, had formed an early object 
of Mr. Watt’s attention, and he had deeply considered the 
various means of effecting this. This he accomplished by 
a series of improvements, the exclusive property of which 
he secured by successive patents in the years 1781, 1782, 
1784, and 1785; including, among other inventions, the 
rotatory motion of the sun and planet wheels, the expansive 
principle, the double engine, the parallel motion, and the 
smokeless furnace. The application of the centrifugal regu¬ 
lating force of the governor gave the finishing stroke to the 
machine.- 
The invention of the separate condensor, and the contri¬ 
vances necessary to give it full effect, would alone have es¬ 
tablished the fame of Mr. Watt; but when to these are added 
the various inventions called forth to perfect his rotative 
engines, we are impressed by a union of philosophical re¬ 
search, of physical skill, and of mechanical ingenuity, which 
has, we believe, no parallel in modern times. 
The perfection thus given to the rotative engine soon led 
to its general application for imparting motion to almost 
every species of mill-work and machinery; and gave an im¬ 
pulse, unexampled in the history of inventions, to the ex¬ 
tension of our manufactures, population, and wealth. 
Nor were Mr. Watt’s inventive powers confined to the 
steam-engine. The necessity of preserving accurate copies 
of his various drawings and of his letters, containing long 
and important calculations; and the desire of avoiding that 
labour himself, which he did not think it right to entrust to 
others, led him, in the year 1780, to contrive a copying ap¬ 
paratus, the exclusive property in which he secured by Let¬ 
ters Patent, and commenced the manufactory of them in 
partnership with Mr. Boulton, and his friend, Mr. Keir, un¬ 
der the firm of James Watt and Company;—a contrivance 
of great simplicity, and of which he reaped an ample benefit 
in the time, labour, and expence it saved to himself, to say 
nothing of its advantages to the public. 
In the winter of 1784-5, he put up an apparatus for heating 
the room in which he drew and wrote by means of steam. 
The possibility of doing this we find suggested by Colonel 
Cooke, in the Philosophical Transactions for 1745 ; but we 
know not whether this was known to Mr. Watt when he 
made his first practical attempt, from which he deduced pro¬ 
portions of surface, &c., which afterwards served to guide 
his firm in the introduction of the process in larger build¬ 
ings. 
Chemical studies engaged much of his attention during 
his busiest time, and at the very period w hen he was most 
engaged in perfecting his rotative engines, and in managing 
a business become considerable, and, from its novelty, re¬ 
quiring close attention, he entered deeply into the investiga¬ 
tions then in progress relative to the constitution and pro¬ 
perties of the different gases. 
Mr. Watt also has the merit of being the first person to 
introduce into this country, and to carry into effect, on a 
practical scale, in any country, the bleaching of linens and 
cottons by oxymuriatic acid, the invention of his friend, Mr. 
Berthollet. That gentleman had communicated his inven¬ 
tion to Mr. Watt, at Paris, in the winter of 1786-7, whither he 
had proceeded with Mr. Boulton at the instance of the French 
government, to suggest improvements in the mode of raising 
water at Marly, and his mind was instantly alive to the ex- 
6 H tensive 
