80 THE PRINCIPT-ES OF SCIENCE. [chap. v. 



which contains a full description of "this specimen," as 

 furnished in the premises, but by ellipsis asserts tliat it is 

 gold. It will be observed that iu the symbolic expression 

 (i) I have explicitly stated wliat is certainly implied, that 

 copper is not gold, and gold not copper, without which 

 condition the inference would not hold good. 



