the vividness and truth of this representation. So conceived, it is seen to distinguish not poets only, but men of science; for in them, too, "imagination bodies forth the forms [and actions] of things unknown" It does this in an equal, and sometimes even in a higher degree; for, strange as the assertion will seem to most, it is nevertheless true that the mathematician who discloses to us some previously unknown order of space-relations, does so by a greater effort of imagination than is implied by any poetic creation. The difference lies in the fact that, whereas the imagination of the poet is exercised upon objects of human interest and his ideas glow with emotion, the imagination of the mathematician is exercised upon things utterly remote from human interest, and which excite no emotion: the contrasted appreciations of their respective powers being due to the circumstance that whereas people at large can follow, to a greater or less extent, the imaginations of the poet, the imaginations of the mathematician lie in a field inaccessible to them, and practically non-existent.
This constructive imagination (for we are not concerned with mere reminiscent imagination), here resulting in the creations of the poet and there in the discoveries of the man of science, is the highest of human faculties. With this faculty Prof. Tyndall was largely endowed. In common with successful investigators in general, he displayed it in forming true conceptions of physical processes previously misinterpreted or uninterpreted; and, again, in conceiving modes by which the actual relations of the phenomena could be demonstrated; and, again, in devising fit appliances to this end. But to a much greater extent than usual, he displayed constructive imagination in other fields. He was an excellent expositor; and good exposition implies much constructive imagination. A pre-requisite is the forming of true ideas of the mental states of those who are to be taught; and a further pre-requisite is the imagining of methods by which, beginning with conceptions they possess, there may be built up in their minds the conceptions they do not possess. Of constructive imagination as displayed in this sphere, men at large appear to be almost devoid; as witness the absurd systems of teaching which in past times, and in large measure at present, have stupefied, and still stupefy, children by presenting abstract ideas before they have any concrete ideas from which they can be drawn. Whether as lecturer or writer. Prof. Tyndall carefully avoided this vicious practice.
In one further way was his constructive imagination exemplified. When at Queenwood College he not only took care to set forth truths in such ways and in such order that the comprehension of them developed naturally in the minds of those he taught—he did more: he practiced those minds themselves in construct-