He found out the simple fact that smoke will readily go up a chimney, unless there is something to stop it. All that was necessary was to discover the trouble and remove it. In nearly all of the five hundred chimneys nothing more was needed than to make the lower part of the chimney and the fireplace of the right form and size. One firm of builders was kept constantly employed carrying out his suggestions. Not only did he "cure" the chimneys, but he also prevented the waste of much heat. In accordance with his directions the square fireplace was changed so that the sides made a greater angle with the back and would therefore reflect more heat into the room. He also made the space about the fire smaller, thus rendering the air hotter and therefore more ready to rush up the chimney, carrying more of the smoke with it. Count Rumford's ideas have been generally followed since his day, and now fireplaces seldom give out smoke into the room while they furnish more heat. Count Rumford next took up the problem of improving stoves. Before we consider his improvements, however, we must note something about the first stoves. Another Massachusetts boy, born nearly half a century before Benjamin Thompson, also became a scientist, inventor, and discoverer. Benjamin Franklin was a traveler and in many other respects was like Count Rumford. But he chose to go with the colonies when they revolted from Great Britain, and he gave all his services to his fellow countrymen. A few years before the birth of Thompson, Franklin made an invention which was the first improved method of heating rooms. There had been so-called German stoves before his day, but they were not much used in this country. [Illustration: A FRANKLIN STOVE.] It was in 1742 that Franklin, while in Philadelphia, devised the "Franklin stove" or "Pennsylvania fireplace." It consisted of iron sides, back and top, and was entirely open in front. A flue was arranged in the back which connected with the chimney to carry off the smoke. This movable fireplace was designed to burn wood, comparatively small logs being used. It had many advantages over the stone fireplace. It was set up nearer the middle of the room, thus sending heat out in all directions and warming the entire room. It saved much of the heat which had previously passed directly up the chimney and been lost. In the Pennsylvania fireplace this heat warmed the iron on the top of the stove and at the back, as well as the flue itself, all of which warmed the air in the room. Saving the heat saved wood also. Franklin himself said: "My common room, I know, is made twice as warm as it used to be, with a quarter of the wood I formerly consumed there."