832 
PROCEEDINGS OF THE SOCIETY. 
The President said he had, with great regret, to record the deaths 
of two Honorary Fellows of the Society — Mr. Kitchen Parker and Mr 
Balfs. The former gentleman was so well known to them by the work 
which he accomplished, and for the enthusiasm with which he 
entered upon his researches, as well as from haying been at 
one time President of their Society, that it was unnecessary for him to 
refer to him at any length on that occasion. They would all feel that, 
in losing him, they had lost a very valuable friend and fellow worker. 
Mr. Ealfs w r as elected an Honorary Fellow of the Society only a short 
time ago, and, in fact, died before he had received an intimation of his 
election. In place of these two gentlemen, the Council had nominated 
as Honorary Fellows — Dr. Henry Brady and Prof. Williamson, FF.E.S. 
Eeferring to the explanation he had given at the June meeting 
regarding the new objective of 1 • 6 N. A., presented to the Society by the 
firm of Carl Zeiss, of J ena, Mr. Mayall said he must ask the indulgence 
of the meeting to enable him to clear himself from possible ambiguity. 
In notifying the fact that at the first photographic trials of the objective, 
the visual and actinic foci were found by Mr. Nelson and himself to be 
not coincident, and that when the objective was returned to Jena im- 
mediately after, Dr. Czapski, of the firm of Zeiss, found the foci were 
coincident, the explanation of the extraordinary divergence on the 
point seemed to him of the nature of a puzzle, which, for the moment, 
appeared inexplicable. He had, therefore, hazarded what he had ima- 
gined would appear a mere playful admission of the state of general 
puzzlement of both sides by suggesting that the transit of the objective 
from London to Jena had somehow got rid of the “ chemical ” focus. 
That sentence had unhappily been construed, both in England and 
abroad, into a reflection upon the good faith of Dr. Czapski, or upon 
Dr. Abbe, or upon the firm of Zeiss. Whatever blame was due to him- 
self for the ambiguity of the expression, he must of course accept. At 
the same time he thought the Society would be interested to learn that 
upon his conveying his explanation to Dr. Czapski and Dr. Abbe, those 
gentlemen had expressed their complete satisfaction with it. The inter- 
change of correspondence on the subject had led him to consider closely 
the whole circumstances, and he believed the existence of the “ chemical ” 
focus was probably due to a slight difference in the adjustment of the 
front lens, the mounting of which was partially unscrewed from the body 
of the objective when it first reached his hands, and which he might 
not have set exactly in the normal position in which it left Jena. On 
his suggesting this explanation of the difficulty to Dr. Abbe, its possi- 
bility was at once admitted, especially, as Dr. Abbe pointed out, in view 
of the fact that with an objective of such large aperture the colour-cor- 
rection was, as it were, “ balanced on a needle-point ” in the matter of 
an alteration in the distance of the front lens from the posterior 
combinations ; and that a very minute alteration in that distance, though 
producing no perceptible difference in the visual image, was quite 
competent to lengthen or shorten the focus of the violet rays to such an 
extent as to exhibit a “ chemical ” focus non-coincident with the visual 
focus when tested photographically. It appeared that when the objective 
was returned to Jena, it was not examined optically in the precise con- 
