If one ","ere to tell the 'ordinary labourer that water is composed of two gases which

when combined form a liquid, he would probably be quite incredulous, and possibly in his ignorance might even deny emphatically any such possibility, on the grounds that it was against all common-sense and experience; he failing to realise, of course, how very limited were both his sense and his experience. In spite of his feelings of absolute certainty, and in spite of complete faith in the unshakable logic behind his belief, he would be wrong.