THE president's ADDRESS. 195 



after, resumed the study of entoptics so far as to gain a hearing", 

 the stereotyped history of its methods wotdd never have been 

 challenged through it. 



Through Mackenzie's annotations, I have been enabled to 

 amend the history of Helmholtz in favour of an Englishman in 

 more than one particular, though I have never done so without 

 the precaution of consulting the original authority myself. In 

 the solitary instance of the suggestion I have to-day associated 

 with Capt. Kater's name, I left the authorship undetermined; 

 because having to go through Mackenzie's references seriation, in 

 the library of the British Museum, in order to discover from whom 

 he had derived it, I was unable to trace it to its author until it 

 was too late to do him justice in the monograph. The contin- 

 gency that facts may yet come to light to upset more or less of 

 this history, or that facts already before the world may yet be 

 differently estimated by another commentator — by Helmholtz 

 himself, say — has no bearing on my present purpose. I am not 

 now working up the history of a subject ; but offering the story 

 I have just told as an epitome of the flaws that often betray 

 themselves in fabrics constructed from literary materials ; though 

 they may have commonly been esteemed as substantially built 

 from sure foundations. 



The interval between this and last year's Spring Meeting has 

 been more than ordinarily prolific in incidents of such general 

 scientific interest as kindle discussion in great national societies, 

 and animate current literature, so that the sole puzzle in com- 

 posing an address from them would be that of selecting the 

 threads out of which the texture should be woven. But the 

 very fact that information upon such topics is, in our day, 

 reproduced in every possible guise, and, as it were, dropped 

 gratituously into all our letter boxes, seems to me a reason why 

 I should refrain from enlarging upon them in a local society, and 

 I have preferred running the risk of being regarded as egotistical 

 rather than, on this occasion, make them the main sources of my 

 remarks. But I shall append a bare mention of a few of the 

 leading incidents which have lately been exciting the attention 

 of all intelligent minds. 



Foremost among them have been the observations of the transit 

 of Venus over the Sun's disc, as giving us a rare opportunity of 



