THREE:She was sitting in her room, sewing. Of late she had become domesticated, and she was fading under it. He had seen it already, and he saw it more plainly than ever just now. She looked up and smiled. Her smile had always been one of her greatest charms, because it was rare and very sweet. "Jack," she greeted him, "what have you done with the bread knife you took with you, dear? I have been lost without it."On the laws of heat and cold, and atmospheric changes under their influence, many interesting facts were ascertained by the aid of the thermometers of Fahrenheit and Raumur. Dr. Martin, of St. Andrews, distinguished himself in these inquiries, and published his discoveries and deductions in 1739 and 1740. In 1750 Dr. Cullen drew attention to some curious facts connected with the production of cold by evaporation. Dr. Joseph Black discovered what he called latent heat, and continued his researches on this subject beyond the present period.
