THE president's ADDRESS. 185 



most of the cases, how few of the writings they name they have 

 themselves perused. As if minds that find pleasure in original 

 scientific investigations have no time to spare for gathering 

 materials for the histories of the subjects that are dear to them ; 

 or even to carefully inspect the materials that others have cast in 

 their paths. However this may be, the lack of such histories 

 from competent hands is the cause of many a halt or other 

 incongruity in the onward-march, I suspect, of all the sciences. 

 In the course of my casual reading, I am ever and anon coming 

 across curious illustrations of this statement, but it is from the 

 domain of physiological optics that I shall to-day offer a few 

 facts in justification of what I have said. Because there are 

 certain portions of this subject, whose history I have taken much 

 pains to fathom, that present facts so fitting for my purpose that 

 I need not look around in quest of others. 



It may be half-a-dozen years ago I stumbled upon a paragraph 

 in some popular address, delivered in Germany, by, unless my 

 memory betrays me, no less an authority than Professor H. 

 Hehnholtz, in which it was declared that the Baconian Lecture 

 delivered before the Royal Society in the year 1800 by Dr. 

 Thomas Young, is one of the grandest contributions to physio- 

 logical optics ever made, but that strange to say, the English 

 themselves seemed quite unconscious that they possessed such a 

 treasure ! For my humble part, I had held the said lecture in 

 such reverence as to have ascribed to it in print the foundation 

 of such knowledge of the subject as I had been able to acquire. 

 I could not help surmising that it was the orator himself, who 

 had so lent his thoughts to like investigations as only just then 

 to have awakened to the consciousness that he had had so 

 formidable a precursor in a like career that an immediate study 

 of his celebrated lecture could no longer be dispensed with. 



Even in 1866, in penning the preface to his Handbuch der 

 physiologischen Optik, which had been ten years going through 

 the press as a portion of the Encyclopaedia already mentioned, 

 Helmholtz, after saying that he had turned all the means at his 

 disposal to account to render the literary retrospects contained in 

 the work trustworthy, adds, as I translate his words: — "The 

 newer literature will be tolerably complete ; the older, in a great 

 degree, I have been obliged to gather from secondary sources, 



