inquiries far beyond the range of his senses. From facts that appeal to his senses he reasons as to phenomena that can never be directly observed, and by intellectual processes he can acquire knowledge as accurate as if he were able to examine the phenomena with organs of sense having powers much more extensive than those he possesses. A recognition of this quality of man's mind indicates also the value of education in science. This does not consist, as is often erroneously supposed, in merely acquiring a knowledge of fact, but also and more in learning to reason correctly and in cultivating the use of the imagination. The scientific thinker has a mental vision into regions far beyond the limited powers of his senses, and hence there is much truth in the statement that the greatest scientific men have many of the qualities of mind of the poet or of the prophet. They are seers in a true sense of the word.
Let us take another simple experiment or two from the region of physics, to prepare the way for our own special study. Here is a mass of soft iron, like the half of a link of a large chain. Copper wire has been coiled round each
