was introduced into a tube of brass, with as much water round it as to fill the tube. The apparatus was then plunged into a vessel of boiling water, or heated to boiling point; when the total expansion of the bar was measured by a graduated scale, as seen in the annexed engraving. By this simple means the expansion of any material might be ascertained under various increments of heat, say from 60deg to 2l2deg It was simply a thermometer, the mass marking its own expansion. Dr. Brewster was so much pleased with the apparatus that he described it and figured it in the Edinburgh Philosophical Journal, of which he was then editor.

The road steam-carriage. By James Nasmyth.

About the year 1827, when I was nineteen years old, the subject of steam carriages to run upon common roads occupied considerable attention. Several engineers and mechanical schemers had tried their hands, but as yet no substantial results had come of their attempts to solve the problem. Like others, I tried my hand. Having made a small working model of a steam-carriage, I exhibited it before the members of the Scottish Society of Arts. The performance of this active little machine was so gratifying to the Society that they requested me to construct one of such power as to enable four or six persons to be conveyed along the ordinary roads. The members of the Society, in their individual capacity, subscribed £60, which they placed in my hands as the means for carrying out their project.

I accordingly set to work at once. I had the heavy parts of the engine and carriage done at Anderson's foundry at Leith. There was in Anderson's employment a most able general mechanic named Robert Maclaughlan, who had served his time at Carmichaels' of Dundee. Anderson possessed some excellent tools, which enabled me to proceed rapidly with the work. Besides, he was most friendly, and took much delight in being concerned in my enterprise. This "big job" was executed in about four months. The steam- carriage was completed and exhibited before the members of the Society of Arts. Many successful trials were made with it on the queensferry Road, near Edinburgh. The runs were generally of four or five miles, with a load of eight passengers sitting on benches about three feet from the ground.

The experiments were continued for nearly three months, to the great satisfaction of the members. I may mention that in my steam-carriage I employed the waste steam to create a blast or draught by discharging it into the short chimney of the boiler at its lowest part, and found it most effective. I was not at that time aware that George Stephenson and others had adopted the same method; but it was afterwards gratifying to me to find that I had been correct as regards the important uses of the steam blast in the chimney. In fact, it is to this use of the waste steam that we owe the practical success of the locomotive- engine as a tractive power on railways, especially at high speeds.

The Society of Arts did not attach any commercial value to my steam road-carriage. It was merely as a matter of experiment that they had invited me to construct it. When it proved successful they made me a present of the entire apparatus. As I was anxious to get on with my studies, and to prepare for the work of practical engineering, I proceeded no further. I broke up the steam-carriage and sold the two small high-pressure engines, provided with a compact and strong boiler, for £67, a sum which more than defrayed all the expenses of the construction and working of the machine.

I still continued to make investigations as to the powers and capabilities of the steam-engine. There were numerous breweries, distilleries, and other establishments, near Edinburgh, where such engines were at work. As they were made by different engineers, I was desirous of seeing them and making sketches of them, especially when there was any special peculiarity in their construction. I found this a most favourite and instructive occupation. The engine tenters became very friendly with me, and they we re always glad to see me interested in them and their engines. They were especially delighted to see me make "drafts," as they called my sketches, of the engines under their charge.

My father sometimes feared that my too close and zealous application to engineering work might have a bad effect upon my health. My bedroom work at brass casting, my foundry work at the making of steam-engines, and my studies at the University classes, were perhaps too much for a lad of my age,