part 1] AlfNIVERSABY ADDRESS OF THE PRESIDENT. Xci 



resemblance fco thrusting in the ordinary sense of the word ; the 

 inovement would not be like tliat of a sledge, pushed bodily 

 forward over the ground, but more akin to the crawl of a cater- 

 pillar which advances one part of its l^od}'' at a time, and all parts 

 in succession. A further result is that the motive power would 

 liave originated within the area of the overthrust, and, as we 

 cannot conceive of this taking place in the dead rock of the upper 

 block involved, we must put it in the lower one, more directh' 

 associated with those lower layers of the crust, in which many 

 imperfectly understood changes are cei'tainly going on, and pro- 

 bably many that are wholly unsuspected at present. 



Without entering into advocacy of this hj'^pothesis of origin of 

 ovei'thrusts, the claim must at least be made that it is a possible 

 one, consistent with the facts revealed by observation, and not 

 incompatible with our present knowledge, or ignorance, of the 

 physics of the Earth's crust. If accepted, it follows that the word 

 'overthrust' suggests something quite different from what 

 actually took place, and that the Avord ' undercra wl ' would more 

 nearly express the manner in which tlie thing referred to was 

 brought al)Out ; yet I have no desire, certainly no intention, to 

 suggest that a well-established term should be abandoned and 

 replaced by one which may be just as misleading, if we define it 

 otherwise than as a reversed fault of very low inclination from the 

 liorizontal. So long as the connotation is thus limited, one word 

 is as good as another, and when, wishing to discuss origins and 

 processes of formation, we go beyond this meaning, all words m.B.y 

 be equally bad, if we allow collateral meanings of the constituent 

 parts to influence our reasoning. 



The theme might be expanded indefinitely, but enough has been 

 said to point the moral, of tlie danger of loose use of words, and of 

 the necessitj^ of distinguishing clearly between things themselves 

 and the terms in which they are described or mentioned. The 

 lesson is no new one, for the fallacy, of using the same word in 

 more than one sense, must be as old as language and logic ; it is 

 so well known that, for over 2000 years logicians have used a 

 special term to describe, and have consistently warned us to avoid, 

 it, yet, old as it is, it is ever new, and the warning needs repeated 

 reiteration, for it is a form of fallac}^ to which mankind is natur- 

 ally prone, and almost impossible of avoidance, in the finite 



