"[A]ir is a which has weight as well as others, though about eight hundred times lighter than water; that heat makes the particles of air recede from each other and take up more space, so that the same weight of air heated will have more bulk [volume] than equal weights of cold air which may surround it, and in that case must rise, being forced upwards by such colder and heavier air, which presses to get under it, and take its place."