The continued and increasing success of the Soho works was obviously owing to the new partners. They had some excellent assistants, but in the foremost place among all of them stands Murdoch, Watt's able, faithful and esteemed assistant for many years, who, both intellectually and in manly independence, was considered to exhibit no small resemblance to his revered master and friend. Never formally a partner in Soho (for he declined partnership as we have seen), he was placed on the footing of a partner by the sons in 1810, without risk, and received $5,000 per annum. From 1830 he lived in peaceful retirement and passed away in 1839. His remains were deposited in Handsworth Church near those of his friends and employers, Watt and Boulton (the one spot on earth he could have most desired). "A bust by Chantrey serves to perpetuate the remembrance of his manly and intelligent features, and of the mind of which these were a pleasing index." We may imagine the shades of Watt and Boulton, those friends so appropriately laid together, greeting their friend and employee: "Well done, thou good and faithful servant!" If ever there was one, Murdoch was the man, and Captain Jones his fellow.
We have referred to Watt's suggestion of the screw-propeller, and of the sketch of it sent to Dr. Small, September 30, 1770. The only record of any earlier suggestion of steam is that of Jonathan Hulls, in 1736, and which he set forth in a pamphlet entitled "A Description and Draught of a Newly Invented Machine for carrying vessels or ships out of or into any Harbour, Port or River, against Wind or Tide or in a Calm"; London, 1737. He described a large barge equipped with a Newcomen engine to be employed as a tug, fitted with fan (or paddle) wheels, towing a ship of war, but nothing further appears to have been done. Writing on this subject, Mr. Williamson says:
During his last visit to Greenock in 1816, Mr. Watt, in company with his friend, Mr. Walkinshaw—whom the author some years afterward heard relate the circumstance—made a voyage in a steamboat as far as Rothsay and back to Greenock—an excursion, which, in those days, occupied a greater portion of a whole day. Mr. Watt entered into conversation with the engineer of the boat, pointing out to him the method of "backing" the engine. With a footrule he demonstrated to him what was meant. Not succeeding, however, he at last, under the impulse of the ruling passion, threw off his overcoat, and, putting his hand to the engine himself, showed the practical application of his lecture. Previously to this, the "back-stroke" of the steamboat engine was either unknown, or not generally known. The practice was to stop the engine entirely a considerable time before the vessel reached the point of mooring, in order to allow for the gradual and natural diminution of her speed.
The naval review at Spithead, upon the close of the Crimean war in 1856, was the greatest up to that time. Ten vessels out of two hundred and fifty still had not steam power, but almost all the others were propelled by the screw—the spiral oar of Watt's letter of 1770—a red-letter day for the inventor.
Watt's early interest in locomotive steam-carriages, dating from Robison's having thrown out the idea to him, was never lost. On August 12, 1768, Dr. Small writes Watt, referring to the "peculiar improvements in them" the latter had made previous to that date. Seven months later he apprises Watt that "a patent for moving wheel-carriages by steam has been taken out by one Moore," adding "this comes of thy delays; do come to England with all possible speed." Watt replied "If linen-draper Moore does not use my engine to drive his chaises he can't drive them by steam." Here Watt hit the nail on the head; as with the steamship, so with the locomotive, his steam-engine was the indispensable power. In 1786 he states that he has a carriage model of some size in hand "and am resolved to try if God will work a miracle in favor of these carriages." Watt's doubt was based on the fact that they would take twenty pounds of coal and two cubic feet of water per horse-power on the common roads.
Another of Watt's recreations in his days of semi-retirement was the improvement of lamps. He wrote the famous inventor of the Argand burner fully upon the subject in August, 1787, and constructed some lamps which proved great successes.
The following year he invented an instrument for determining the specific gravities of liquids, which was generally adopted.
One of Watt's inventions was a new method of readily measuring distances by telescope, which he used in making his various surveys for canals. Such instruments are in general use to-day. Brough's treatise on "Mining" (10th ed., p. 228) gives a very complete account of them, and states that "the original instrument of this class is that invented by James Watt in 1771."
In his leisure hours, Watt invented an ingenious machine for drawing in perspective, using the double parallel ruler, then very little known and not at all used as far as Watt knew. Watt reports having made from fifty to eighty of these machines, which went to various parts of the world.
In 1810 Watt informs Berthollet that for several years he had felt unable, owing to the state of his health, to make chemical experiments. But idle he could not be; he must be at work upon something. As he often said, "without a hobby-horse, what is life?" So the saying is reported, but we may conclude that the "horse" is here an interpolation, for the difference between "a horse" and "a hobby" is radical—a man can get off a horse.