Vlll PREFACE. 



Seeing then the magnitude of the subjects touched upon, 

 all that I can venture to draw from the papers I have 

 written must be desultory in character, and very imperfect 

 in its handling of each. All that I can expect to afford is 

 a summary of our actual knowledge on some of these great 

 topics, denoting especially what may be considered truths 

 conclusively proved, as distinguished from what is hypo- 

 thetical or presumptive only. Much, probably more than 

 we care to acknowledge, comes under the latter head . . . 



Witli this unfinished sentence the pen of my Father 

 was laid down for ever; and -that these closing words 

 are thoroughly characteristic, will be felt by every 

 reader of the Essays here brought together. Sentence 

 after sentence could be quoted from them, as also from 

 his other writings, to show how he understood, and 

 ever earnestly taught, that ' those whose researches 

 and thoughts go deepest are best prepared to en- 

 dorse the words of Laplace, "Notre ignorance est 

 immense," as the expression of a truth underlying 

 all our knowledge.' 



I feel that no further preface is needed for these 

 Essays. As they were left in the MS., so are they 

 now printed for the first time without any material 

 alteration. 



To the papers not hitherto published have been 

 added three reviews which Sir Henry contributed to 

 the 'Edinburgh Eeview ' in the years 1864, 1871, and 

 J873. 



FRANCIS J. HOLLAND. 



