Page:The fairy tales of science.djvu/205

Rh apparent anomaly is easily explained. The intense heat of the melted metal instantly vaporizes the moisture of the hand, and the experimentalist receives no injury, as his hand is protected by a thick glove of non-conducting steam. It is highly probable that the priests of old were acquainted with this fact, and made good use of it in the ordeal of fire. When a person was accused of some crime which could not be proved against him, he was subjected to the fiery ordeal, that is to say, he had to plunge his arm into molten lead or walk barefooted over red-hot ploughshares. If he passed through the ordeal scathless, his innocence was held to be satisfactorily established. Now the reader need not be told that the safety of the suspected person did not depend on his freedom from guilt but on the moisture of his arm or feet and the heat of the metal. The greatest criminal might walk over hot ploughshares, provided they were hot enough to give him sandals of vapour. Truly the humble tea-kettle is wonderfully suggestive. We had almost forgotten that it forms the text of the present chapter, but just now the water boiled over and reminded us that we had not touched upon those grand kettles of nature, the Geysers, or intermittent boiling fountains of Iceland. The Geysers, of which there are a considerable number, are springs of hot water holding a large quantity of silex or flint in solution, which issue