None of the children knew.
Father. "Water would boil the soonest. More heat is necessary to make oil boil, or turn into vapour, than to make water evaporate. Do you know of any thing which is used to determine, to show, and mark, to us the different degrees of heat?"
B——. "Yes; a thermometer."
Father. "Yes: thermometer comes from two Greek words, one of which signifies heat, and the other measure. Meter, means measure. Thermometer a measurer of heat; barometer, a measurer of the weight of the air; hygrometer, a measurer of moisture. Now, if you remember, on the thermometer you have seen these words at a certain mark, the heat of boiling water. The quicksilver, in a thermometer, rises to that mark when it is exposed to that degree of heat which will make the water turn into vapour. Now the degree of heat which is necessary to make oil evaporate, is not marked on the thermometer; but it requires several degrees more heat to evaporate oil, than is necessary to evaporate water.—So now you know that chocolate, containing more oil than is contained in tea, it can be made hotter before it turns into vapour."
Children may be led to acquire a taste for chemistry by slight hints in conversation.
(July 22d, 1794.) Father. "S——, can you tell me what is meant by a body's falling?"
S—— (seven years old.) "A body's falling, means a body's dying, I believe."
Father. "By body, I don't mean a person, but any thing. What is meant by any thing's falling?"
S——. "Coming down from a high place."
Father. "What do you mean by a high place?"