PROFESSOR TYNDALL. 341 



region of physics to that of thought, we meet a 

 problem not only beyond our present powers, but 

 transcending any conceivable expansion of the 

 powers we now possess. We may think over the 

 subject again and again, but it eludes all intel- 

 lectual presentation. The origin of the material 

 universe is equally inscrutable. Thus, having ex- 

 hausted science, and reached its very rim, the real 

 mystery of existence still looms around us. And 

 thus it will ever loom ever beyond the bourne of 

 man's intellect giving the poets of successive ages 

 just occasion to declare that 



" We are such stuff 



As dreams are made of, and our little life 

 Is rounded by a sleep.' " 



Professor Tyndall did not, in 1868, look hope- 

 fully forward to the possibility of an experi- 

 mental inquiry as to the causes of mentation or the 

 faculty of the brain to produce mind. I think the 

 methods of inquiry proposed in chap. xix. are 

 analogous, not to say copied from, the modes used 

 by the physicists. It may be maintained that the 

 work entitled "Heat a Mode of Motion" chiefly 

 deals with the obvious expressions of heat in a 

 manner very analogous to that in which we propose 

 to study mind, by observing and experimenting 

 with the forces producing "mentation." To illus- 

 trate this, quotations are taken from the "con- 

 tents " of the volume referred to : 



I. Instruments; II. The nature of heat; III. 

 Expansion ; IV. The Trevelyan instrument ; V. Ap- 

 plication of the dynamical theory ; VI. Convection 



