Page:Dictionary of National Biography volume 60.djvu/67

 to the greater or less approach to a perfect vacuum which could be effected; but as the pressure of steam became increased, the value of the vacuous condition became relatively less and less, and thus the finality so confidently claimed by Mr. Serjeant Rous, in his speech to the court of appeal, was speedily shown to be groundless. Rous asserted, ‘This peculiar invention, for which this patent has been obtained, was from the first perfect and complete, has never been improved, and from the nature of things never can, because it is impossible to have more than all.’ So long ago as 1872, at the Cardiff meeting of the Royal Agricultural Society before mentioned, a portable non-condensing engine was shown, developing a horse-power for a consumption of 2.79 lb. of coal per hour.

It has always been a matter of surprise that Watt, who had invented the expansive use of steam, did not develop this principle by employing steam of higher and higher initial pressure; but this he did not do, and he steadily opposed Richard Trevithick [q. v.], who was the persistent advocate of high-pressure steam coupled with expansion. Sixteen years after Watt's death, when the writer of this article was an apprentice, the common pressure of steam in condensing engines, whether stationary or marine, was from 4 to 6 lb. per square inch above atmosphere; and notwithstanding the condensation in the separate vessel, the consumption of coal was from 5 to 8 lb. per horse-power per hour. The steam pressure in marine engines is now from 150 to 250 lb. (Perkins went as high as 500 lb.), and the consumption of coal is from 1½ to 2½ lb. per horse-power per hour.

In spite of his wretched health, Watt was one of the most determined and persistent of men; his courage, except in matters of finance, was of the highest. He very early acquired a knowledge of German and of Italian to enable him to read works on mechanics published in those languages, and he appears from his correspondence to have been a good French scholar. It has been said he was originally a mathematical instrument maker, and a workman of great delicacy of touch. In his early days at Glasgow, at the request of some friends, he made an organ of great beauty of tone, and he also made other musical instruments to oblige his friends, and not, it would appear, from a love of music; for in later years, when Southern applied for employment at Soho, Watt said: ‘I should be very glad to engage him for a drawer, provided he gives bond to give up music. Otherwise I am sure he will do no good, it being the source of idleness.’ In early days also Watt invented and sold a portable machine for drawing from nature in proper perspective.

In his chemical pursuits he not only devised the apparatus to manufacture the ‘factitious airs,’ but he invented a simple mode of ascertaining the specific gravity of fluids, by means of a tube terminating in two tubular legs, one of which was immersed in distilled water, the other in the liquid to be tested. A partial exhaustion of the single tube being made, the water and the liquid to be tested rose in the respective legs, and the differences in the height between that of the water and of the liquid under trial gave the specific gravity of this liquid as compared with the water. Watt also invented an admirable micrometer; and he perceived the value of weather records, and for nine years kept at Soho a most complete account, observing every day at eight in the morning, two in the afternoon, and eight in the evening the height of the barometer, the temperature, the hygrometer, the direction of the wind, the rainfall, and the general condition of the weather.

Reverting to engineering—Watt devised a locked-up automatic counter, to record the number of strokes made throughout lengthened periods by his pumping engines. He proposed, and included in his patent of 1784 (No. 1432), a steam carriage for common roads, with differential gear for use on hills. He also proposed the use of the screw propeller, which he called the ‘spiral oar,’ for navigation. He was, in truth, not a mere specialist devoted to one subject, but was of great general scientific learning, and was a happy instance of a man who based his inventions on scientific data, and proved them in the model form by aid of his rare manual dexterity.

As regards the favourable impression he made on those with whom he associated in his later life, and the extent and versatility of his information, nothing can more readily testify to this than the statement by Sir Walter Scott of his meeting with Watt in 1817, when Watt was in his eighty-second year (Scott erroneously says eighty-fifth); this is to be found in Scott's letter to ‘Captain Clutterbuck’ in ‘The Monastery’ (1851 edit., p. 42).

Watt was made a fellow of the Royal Society of Edinburgh in 1784, of the Royal Society of London in 1785, and an LL.D. Glasgow in 1806, and was everywhere recognised by men of science as one of the foremost among them. This was so not only