Watson was effectively assisted by his two sons, who carried out their father's designs in constructing the wood patterns after which the foundry-men or moulders reproduced their forms in cast iron, while the smiths by their craft realised the wrought-iron portions. Those sons of Mr. Watson were of that special class of workmen called millwrights -- a class now almost extinct, though many of the best known engineers originally belonged to them. They could work with equal effectiveness in wood or iron.

Another foreman in Mr. Patterson's foundry was called Lewis. He had special charge of the iron castings designed for architectural and ornamental purposes. He was a man of great taste and artistic feeling, and I was able even at that time to appreciate the beauty of his designs. One of the most original characters about the foundry, however, was Johnie Syme. He took charge of the old Boulton and Watt steam-engine, which gave motion to the machinery of the works. It also produced the blast for the Cupolas, in which the pig and cast iron scrap was daily melted and cast into the various objects produced in the foundry. Johnie was a complete incarnation of technical knowledge. He was the Jack-of-all-trades of the establishment; and the standing counsel in every out-of-the-way case of managing and overcoming mechanical difficulties. He was the superintendent of the boring machines. In those days the boring of a steam-engine cylinder was considered high art in excelsis! Patterson's firm was celebrated for the accuracy of its boring.

I owe Johnie Syme a special debt of gratitude, as it was he who first initiated me into that most important of all technical processes in practical mechanism -- the art of hardening and temperinq steel. It is, perhaps, not saying too much to assert that the successful practice of the mechanical arts, by means of which man rises from the savage to the civilised state, is due to that wonderful change. Man began with wood, and stone, and bone; he proceeded to bronze and iron; but it was only by means of hardened steel that he could accomplish anything in arms, in agriculture, or in architecture. The instant hardening which occurs on plunging a red-hot piece of steel into cold water may well be described as mysterious. Even in these days, when science has defined the causes of so many phenomena, the reason of steel becoming hard on suddenly cooling it down from a red-heat, is a fact that no one has yet explained. The steel may be tempered by modifying the degree of heat to which it is afterwards subjected. It may thus be toughened by slightly reheating the hardened steel; the resoftening course is indicated by certain prismatic tints, which appear in a peculiar order of succession on its surface. The skilful artisan thus knows by experience the exact point at which it is necessary again to plunge it into cold water in order to secure the requisite combination of toughness and hardness to the steel required for his purposes.

In all these matters, my early instructor, Johnie Syme, gave me such information as proved of the greatest use to me in the after progress of my mechanical career. Johnie Syme was also the very incarnation of quaint sly humour; and when communicating some of his most valued arcana of practical mechanical knowledge he always reminded me of some of Ostade's Dutchmen, by an almost indescribable sly humorous twinkle of the eye, which in that droll way stamped his information on my memory.

Tom Smith was another of my attached cronies. Our friendship began at the High School in 1818. Our similarity of disposition bound us together. Smith was the son of an enterprising general merchant at Leith. His father had a special genius for practical chemistry. He had established an extensive colour manufactory at Portobello, near Edinburgh, where he produced white lead, red lead, and a great variety of colours -- in the preparation of which he required a thorough knowledge of chemistry.Tom Smith inherited his father's tastes, and admitted me to share in his experiments, which were carried on in a chemical laboratory situated behind his father's house at the bottom of Leith Walk.

We had a special means of communication. When anything particular was going on at the laboratory, Tom hoisted a white flag on the top of a high pole in his father's garden. Though I was more than a mile apart, I kept a look-out in the direction of the laboratory with a spy-glass. My father's house was at the top of Leith Walk, and Smith's house was at the bottom of it. When the flag was hoisted I could clearly see the invitation to me to "come down." I was only too glad to run down the Walk and join my chum, and take part with him in some interesting chemical process. Mr. Smith, the father, made me heartily welcome. He was pleased to see his son so much attached to me, and he perhaps believed