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remind my hearers that as, on the one hand, there is no 

 discussion on the Presidential address, and the members 

 as a body express no opinion upon it, so, on the other, 

 the Association cannot fairly be considered as in any 

 way committed to its tenour or conclusions. Whether 

 this immunity from comment and reply be really on 

 the whole so advantageous to the President as might be 

 supposed need not here be discussed ; but suffice it to 

 say that the case of an audience assembled to listen 

 without discussion finds a parallel elsewhere, and in 

 the parallel case it is not always considered that the 

 result is altogether either advantageous to the speaker 

 or conducive to excellence in the discourse. 



Tlieir range But, apart from this, the question of a limitation 

 of subjects. ^^ range in the subject-matter for the Presidential 

 address is not quite so simple as may at first 

 sight appear. It must, in fact, be borne in mind 

 that, while on the one hand knowledge is distinct 

 from opinion, from feeling, and from all other modes 

 of subjective impression ; still the limits of know- 

 ledge are at all times expanding, and the boundaries of 

 the known and the unknown are never rigid or perma- 

 nently fixed. That which in time past or present has 

 belonged to one category, may in time future belong- 

 to the other. Our ignorance consists partly in ignorance 

 of actual facts, and partly also in ignorance of the pos- 

 sible range of ascertainable fact. If we could lay down 

 beforehand precise limits of possible knowledge, the 

 problem of Physical Science would be already half solved. 

 But the question to which the scientific explorer has 

 often to address himself is, not merely whether he is able 

 to solve this or that problem, but whether he can so 

 far unravel the tangled threads of the matter with 



