8zo THE POPULAR SCIENCE MONTHLY. 



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 imagi- 

 nation of the poet is exercised upon objects of human interest and 

 his ideas glow with emotion, the imagination of the mathema- 

 tician is exercised upon things utterly remote from human in- 

 terest, 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 phe- 

 nomena could be demonstrated ; and, again, in devising fit appli- 

 ances 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 construct- 

 ive 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 stupe- 

 fied, 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 exem- 

 plified. When at Queenwood College he not only took care to set 

 forth truths in such ways and in such order that the comprehen- 

 sion of them developed naturally in the minds of those he taught 

 he did more : he practiced those minds themselves in construct- 



