PRELIMINARY OBSERVATIONS. 



The rigorous method, which presides over the whole of this dis- 

 course ; the links of mutual dependance which connect together the 

 whole of the successive propositions ; the cautious severity which dis- 

 tinguishes every single modification under which the argument is pre- 

 sented to us ; these can only be, as it were, dead letters, perpetually 

 illegible to those ill-starred minds which are destitute of all natural 

 or inherent logic, to which truth becomes an object completely stripped 

 of all its fascinating attractions, and which by no one of its peculiar 

 characters can it ever be recognized by such an order of minds. 



In this place, it becomes my duty to enter into a vindication of my 

 brother from another of the reproaches which assailed him, and which, 

 certainly, would be an exceedingly serious one, did he really deserve 

 it. But, at the same time, that I am sensible of the obligation which 

 his memory imposes upon me, I must yet remember that there are 

 considerations of another kind that render this task particularly differ- 

 ent to me in my present peculiar circumstances. Nevertheless I en- 

 tertain the strongest hopes that, in a discussion so purely scientific 

 in its nature, and in which, so far as I am concerned, a feeling of 

 affection will be uppermost towards the learned gentleman of whom I 

 reluctantly become the antagonist, and that character of sobriety 

 and moderation which are most congenial to such a theme will be 

 sacredly maintained, whilst nothing whatever shall escape my pen 

 which may be inconsistent with this sentiment. 



The reproach to which I allude as having been attempted to be fixed 

 on my brother, amounts to nothing less than the accusation that he 

 declined to adopt as certainly proved, when he laid the foundation of 

 his labours on the extinct animals, an ancient speculation, revived in 

 modern times, and which asserted that all the animal species, both 

 those which existed in the earliest times, as well as those which now 

 inhabit our-globe, were produced from one or more primitive species. 



The presumption, therefore, that was entertained on this occasion 

 respecting my brother was this, that his power of comprehension was 

 too limited to allow him to form a conception so vast, and it was 

 thought that he was so addicted to the study of material facts, as to 

 be utterly unable to elevate his mind beyond this humble boundary of 

 observation, thus being in the condition of those who are obliged to 

 keep the eye uninterruptedly fixed on objects that can only be seen in 

 a much nearer position, and who, under such circumstances, at last 

 become deprived of the power of commanding the full extent of the 

 ordinary horizon. I have no means whatever of ascertaining if even 

 the thought of defending himself from this reproach ever entered the 

 mind of my brother. Indeed, there are strong doubts in my mind that 



