E67 



WATT, JAMES. 



WATT, JAMES. 



553 





atmosphere. Thus he practically demonstrated the power of steam 

 used as in modern high-pressure engines, but he soon abandoned 

 these experiments, and appears to have entertained a prejudice 

 against the use of hisjh-pressure steam throughout bis subsequent 

 career. He however described this engine in his specification of 1769, 

 and again in that of 1784, together with a mode of applying it to the 

 moving of wheel-carriages. The eveut to which the commencement 

 of his invaluable discoveries may be most distinctly assigned, took 

 place in the winter of 1763-4, when Professor John Anderson, who 

 occupied the chair of natural philosophy in the University of Glasgow, 

 requested him to examine and repair a small model of Newcomen's 

 steam-engine, which could never be made to work satisfactorily. His 

 sagacity led him to discover and remove the defects of this model, 

 which was subsequently used in the class-room : and by this circum- 

 stance he was led to detect the imperfections of the machine itself, 

 and to investigate those properties of steam upon which its action 

 depended. About this time he left the college and took up his abode 

 in the town previous to his marriage with his couain, Miss Miller, in 

 the summer of 1764. 



The effective working of Newcomen's machine depended upon two ap- 

 parently irreconcileable conditions : first, that when the cylinder was full 

 of steam, a degree of coldness should be produced within it that should 

 occasion the sudden condensation of the steam, and thereby produce a 

 partial vacuum beneath the piston, which should cause the atmospheric 

 pressure on the upper surface to force it down with sufficient rapidity 

 to give motion to machinery for working a pump ; and, secondly, that 

 immediately after the completion of one stroke the temperature of the 

 cylinder should be again raised to such a degree as to enable it to 

 become refilled with steam preparatory to another stroke. A con- 

 siderable quantity of steam was lost between each stroke in effecting 

 the second object; and when it was accomplished, as the cylinder was 

 too hot to allow the immediate condensation of the steam just admitted, 

 time was lost in cooling it again. Watt calculated that the amount of 

 heat lost from this radical defect of the old, or, as it is usually called, 

 the " atmospheric " steam-engine, was three times as much as was 

 applied to the efficient action of the machine. 



Such was the best, perhaps it is not too much to say the only 

 efficient steam-engine used before the time of Watt ; and notwith- 

 standing its wasteful expenditure of fuel, it was extensively used for 

 the purpose of draining mines. It was thus applied in the collieries 

 in the north of England, in the tin- and copper-mines of Cornwall, 

 and in the lead-mines of Cumberland. Shortly after the middle of 

 the 18th century it was applied to the purpose of raising water to 

 turn water-wheels, and it was used also for "the working of blast- 

 furnaces for smelting iron-ore, and in a few cases for raising water for 

 the supply of towns ; but its use was necessarily limited by the 

 enormous cost of working, as well by its defective and clumsy con- 

 struction. Watt perceived that it was desirable, in order to the 

 efficient use of the steam, that the cylinder should always be kept as 

 hot as the vapour which entered it, to provide for which he had 

 recourse to the beautifully simple expedient of condensing the steam 

 in a separate vessel, which might always be kept cool, and between 

 which and the cylinder a communication might be opened whenever 

 the piston was required to descend. This arrangement being perfected, 

 he next devised means for deriving the fullest possible advantage from 

 it, by maintaining a uniform and high temperature in the cylinder ; 

 an object which be accomplished by enclosing its upper end with a 

 cap or cover, through which the piston-rod could slide freely up and 

 down by means of the air-tight aperture called a stuffing-box, and by 

 employing the elastic force of steam, instead of the pressure of the 

 atmosphere, to depress the piston whenever a partial vacuum was 

 formed beneath it by condensation. The uniform warmth of the 

 cylinder was farther promoted by surrounding it with a 'jacket,' or 

 outer casing, and filling the intervening space between its inner and 

 outer walls with steam. The invention was in its main feature com- 

 pleted as early as 17C5 ; and in the course of his early experiments 

 Watt was much struck by the great heat communicated to the injec- 

 tion-water by which the condensation was effected by a very small 

 quantity of steam, a circumstance which led him by further trials to 

 the discovery that water converted into steam would heat about six 

 times its own weight of water at 47 or 48 to 212. Being struck 

 with, and not understanding the reason of, this remarkable fact, as he 

 himself states in the notes to Robison's ' Mechanical Philosophy,' 

 Watt mentioned it to his friend Dr. Black, who then explained to him 

 his doctrine of latent heat, which he had taught some time previously, 

 although Watt states that he had either not heard of it, or not attended 

 to it when he thus, to use his own words, " stumbled upon one of the 

 material facts by which that beautiful theory is supported." In order 

 to correct an erroneous statement which may have obtained wider 

 circulation than its refutation, we insert a further quotation from the 

 above notes, where Watt observes " Dr. Robison qualifies me as the 

 pupil and intimate friend of Dr. Black, and goes the length of sup- 

 posing me to have professed to owe my improvements upon the steam- 

 engine to the instruction and information I had received from him, 

 which certainly was a misapprehension. He is also mistaken in his 

 assertion that I had attended two courses of the Doctor's lectures. 

 Unfortunately for me, the necessary avocations of my business pre- 

 vented me from attending his or any other lectures at college." 



The marriage of Watt released him from the difficulty which had 

 compelled him to establish himself in the precincts of the college, 

 his wife being the daughter of a freeman. Being thus rendered a 

 freeman himself, he opened a shop in the Salt-market, when his in- 

 creasing business led him to require the labours of an assistant. The 

 success of the first experiments induced Watt to determine upon the 

 construction of a larger model than could be conveniently and pri- 

 vately constructed at his usual place of business, and therefore he set 

 up this machine, with the assistance of his ingenious apprentice, John 

 Gardiner, in one of the rooms of a pottery or ' delft-work,' which he 

 had assisted in establishing near Glasgow, and in which he held a 

 share. An accident terminated his experiments with this engine, 

 which had a cylinder of nine inches diameter, and which, as far as it 

 was worked, proved satisfactorily the practical importance of his im- 

 provements ; and as neither his leisure nor his means enabled him to 

 proceed, the project was for a time laid aside. 



In addition to his employment as a mathematical-instrument maker, 

 Watt devoted much time to the practice of land-surveying, and this 

 led to the employment of his superior talents in the more important 

 departments of civil engineering. Such engagements appear to have 

 occupied much of his attention between the year 1765, when the lead- 

 ing features of his invention were perfected, and 1768, when he found 

 in Dr. John Roebuck, to whom he had become known as a surveyor, 

 an individual capable of appreciating the value of his improvements, 

 and sufficiently enterprising to support him in further experiments. 

 Dr. Roebuck, who is perhaps best known as the founder of the Carron 

 iron-works and the vitriol-works at Prestonpans, was at this time 

 engaged in an extensive colliery undertaking at Kinneil, a few miles 

 from Carron ; and in an outbuilding connected with his residence 

 Watt commenced, in the winter of 1768, a third model, on a much 

 larger scale than either of the preceding. This engine had a cylinder 

 of block tin, eighteen inches in diameter ; and in its construction 

 many difficulties had to be overcome, arising partly from inexperience 

 as to the proportions of the several parts, but mainly from the im- 

 perfect workmanship unavoidable during the infancy of the art of 

 machine-making. One great difficulty consisted in the steam-tight 

 packing of the piston, which could not be effected, as in the old 

 engines, by covering it with a body of water. At length, after eight 

 months' labour, Watt and Roebuck had the satisfaction of seeing the 

 machine in successful operation. The saving of fuel was enormous ; 

 the savin? effected in the supply of water for condensation was little 

 less important, and the result of the experiment fully satisfied 

 Roebuck, who obtained a share in the patent by which Watt secured 

 his inventions. This patent had been applied for in 1768, before the 

 engagement with Roebuck, and it was obtained on the 5th of January 

 1769. The objects embraced in this were as follow : Excluding 

 atmosphere from cylinder keeping cylinder as hot as the steam 

 condensation produced in separate vessels air extracted from con- 

 denser by pumps pistons pressed by the steam a steam-wheel (or 

 rotary engine) partial condensation of steam using oil and wax, 

 instead of water. 



In the summer of that year however the mining speculations of 

 Roebuck involved him in such embarrassments that he was compelled 

 to abandon the experiments with Watt's engine, and Watt himself was 

 therefore obliged to return to his former avocations as an engineer 

 and surveyor (he having relinquished the business of instrument- 

 making in 1768), and to such engagements he chiefly devoted himself 

 until the close of the year 1773. Among the surveys and engineering 

 works in which Watt was engaged before he finally devoted himself to 

 the carrying out of his improvements on the steam-engine was a pro- 

 jected canal between the Forth and the Clyde, by what was called 

 the Lomond passage, in which he was engaged in 1767, when Smeaton 

 was engaged on similar surveys upon a rival line. He also planned 

 and superintended the execution of a canal for conveying the produce 

 of the Monkland collieries to Glasgow. He was engaged upon the 

 Crinan canal, which was subsequently completed by Rennie ; and the 

 deepening of the river Clyde, improving the navigation of the Forth 

 and Devon, and the Water of Leven ; a canal from Machrihanish Bay 

 to Campbeltown ; another from the Grand Canal to the harbour of Bor- 

 rowstownness ; improvements in the harbours of Ayr, Port Glasgow, 

 and Greenock ; and the building of bridges at Hamilton and Ruther- 

 glen, are among the engineering works and projects with which he 

 was connected. Business of this description crowded upon him, and 

 it is stated in the ' Encyclopaedia Britannica ' that his reports are 

 remarkable for their perspicuity and accuracy. In his surveys he 

 used an improved micrometer, and also a machine for drawing in per- 

 spective, both of which he had himself invented. It was while en- 

 gaged on the greatest engineering work undertaken by him, the survey- 

 ing and estimating a line of canal between Fort William and Inverness, 

 since executed by Telford on a larger scale than was then proposed, 

 under the name of the Caledonian Canal, that Watt, in the latter part 

 of the year 1773, received intelligence of the death of his first wife; 

 and he soon afterwards determined to follow the advice of his friend 

 Dr. William Small, of Birmingham, to accept an invitation from 

 Matthew Boulton, the founder of Soho, to settle in England. 



Boulton, to whom Dr. Roebuck transferred his share in the pro- 

 perty of Watt's invention, was a man eminently qualified to bring it 

 into profitable operation; bis energetic and business-like habits 



