As we have read, he had long studied the question of a locomotive steam carriage. In Muirhead's Biography, several pages are devoted to this. In his seventh "new improvement," in his patent of 1784, he describes "the principle and construction of steam engines which are applied to give motion to wheel carriages for removing persons, goods, or other matter from place to place, in which case the engines themselves must be portable." Mr. Murdoch made a model of the engine here specified which performed well, but nothing important came of all this until 1802, when the problem was instantly changed by Watt's friend, Mr. Edgeworth, writing him, "I have always thought that steam would become the universal lord, and that we should in time scorn post-horses. _An iron railroad would be a cheaper thing than a road of the common construction._" Here lay in a few words the idea from which our railway system has sprung. Surely Edgeworth deserves to be placed among the immortals.[3] As in the case of the steamship, however, the indispensable steam engine of Watt had to furnish the motive power. The railroad is only the necessary smooth track upon which the steam engine could perform its miracle. It is significant that steam power upon roads required the abandonment of the usual highway. So we may believe is the automobile to force new roads of its own, or to widen existing highways, rendering those safe under certain rules for speed of twenty miles per hour, or even more, when they were intended only for eight or ten. The reading lamp of Watt's day was a poor affair, and as he never saw an inefficient instrument without studying its improvement, he produced a new lamp. He wrote Argand of the Argand burner upon the subject and for a long time Watt lamps were made at the Soho works, which gave a light surpassing in steadiness and brilliance anything of the kind that had yet appeared. He gives four plans for lamps, "with the reservoir below and the stem as tall as you please." He also made an instrument for determining the specific gravity of liquids, and a year after this he "found out a method of working tubes of the elastic resin without dissolving it." The importance of such tubes for a thousand purposes in the arts and sciences is now appreciated. Watt gave much time to an arithmetical machine which he found exceedingly simple to plan, but he adds, "I have learnt by experience that in mechanics many things fall out between the cup and the mouth." He describes what it is to accomplish, but it remained for Babbage at a much later date to perfect the machine. A machine for copying sculpture amused him for a time but it was never finished.