At his intervals of leisure and in the quiet of his evenings, Watt continued to prosecute his various studies. He was shortly attracted by the science of chemistry, then in its infancy. Dr. Black was at that time occupied with the investigations which led to his discovery of the theory of latent heat, and it is probable that his familiar conversations with Watt on the subject induced the latter to enter upon a series of experiments with the view of giving the theory some practical direction. His attention again and again reverted to the steam-engine, though he had not yet seen even a model of one. Steam was as yet almost unknown in Scotland as a working power. The first engine was erected at Elphinstone Colliery, in Stirlingshire, about the year 1750; and the second more than ten years later, at Govan Colliery, near Glasgow, where it was known by the startling name of “The Firework.” This had not, however, been set up at the time Watt began to inquire into the subject. But he found that the College possessed the model of a Newcomen engine for the use of the Natural Philosophy class, which had been sent to London for repair. On hearing of its existence, he suggested to his friend Dr. Anderson, Professor of Natural Philosophy, the propriety of getting back the model; and a sum of money was placed by the Senatus at the Professor’s disposal “to recover the steam-engine from Mr. Sisson, instrument maker, in London.” In the mean time Watt sought to learn all that had been written on the subject of the steam-engine. He ascertained from Desaguliers, from Switzer, and other writers, what had been accomplished by Savery, Newcomen, Beighton, and others: and he went on with his own independent experiments. His first apparatus was of the simplest possible kind. He used common apothecaries’ phials for his steam reservoirs, and canes hollowed out for his steam pipes.[74] In 1761 he proceeded to experiment on the force of steam by means of a small Papin’s digester and a syringe. The syringe was only the third of an inch in diameter, fitted with a solid piston; and it was connected with the digester by a pipe furnished with a stopcock, by which the steam was admitted or shut off at will. It was also itself provided with a stopcock, enabling a communication to be opened between the syringe and the outer air to permit the steam in the syringe to escape. The apparatus, though rude, enabled the experimenter to ascertain some important facts. When the steam in the digester was raised and the cock turned, enabling it to rush against the lower side of the piston, he found that the expansive force of the steam raised a weight of fifteen pounds with which the piston was loaded. Then, on turning the cock and shutting off the connexion with the digester at the same time that a passage was opened to the air, the steam was allowed to escape, when the weight upon the piston, being no longer counteracted, immediately forced it to descend.