AN ELEMENTARY TREATISE ON HEAT, BY WILLIAM GARNETT, M.A. (LATE WHITWORTH SCHOLAR), FORMERLY FELLOW OF ST JOHN'S COLLEGE, AND DEMONSTRATOR OF IN UNIVERSITY COLLEGE, NOTTINGHAM, AND THE UNIVERSITY OF LONDON. THIRD EDITION, REVISED AND ENLARGED. CAMBRIDGE: DEIGHTON, BELL AND CO. 1. IF we place a poker in a fire, and after some time. remove it, it feels hot. The physical cause of this sensation is called heat. A piece of iron which has been exposed to the air in Britain will generally feel cold. If we hold for some time in the right hand a piece of iron which feels hot, and then grasp the right hand with the left, the left hand will experience a sensation of heat, or the right hand will feel hot to the left, and at the same time the left hand will feel cold to the right. The same will be true if we hold for some time in the right hand any other body which feels hot. The fact that the right hand feels hot to the left after holding the hot iron, while it may have felt neither hot nor cold before, proves that the hand has reIceived heat from the iron. We therefore infer that when a body feels hot to the hand it imparts heat to the hand while touching it. It then follows that, because the right hand feels hot to the left hand, heat must pass from the right hand to the left. But the left hand feels cold to the right hand and associating this sensation with what we have just proved, viz., that heat passes from the right hand to the left, we infer that a body feels cold to the hand when heat passes from the hand to the body. We may arrive at the same conclusion by holding in the right hand a piece of very cold iron, after which the right hand will feel cold to the left, and the left hand warm to the right. Now, the fact that the left hand feels warm to the right, shews that heat |