PROCEEDINGS OF THE SOCIETY. 
393 
was nothing new in the principle, which w’as the same as the Williams’ 
microtome, and the cutting was done with a razor, but the point of 
interest and novelty was the cost. Most kinds of microtomes were, as 
they knew, rather expensive instruments, but the price of this ono was 
3s. 9 d. post free ; or, if with rough plate, 3d. extra (see p. 377). The 
instrument was handed round for inspection by the Fellows present. 
The President said they had received three short papers from Mr. 
Jourdain, which, as the author was not present, he would read to the 
meeting. 
The first of these papers was * On a new Apochromatic Objective 
constructed without the use of fluorite.’ The lenses were made by 
the Bausch and Lomb Optical Company, and Mr. Jourdain promised to 
send a set of them for exhibition at one of the meetings of the Society. 
The President remarked, in connection with this paper, that although 
there was no fluorite used in the manufacture of these lenses, they w r ere 
a great deal more expensive than those made by Messrs. Zeiss, which 
had the fluorite in them. 
Mr. Jourdain’s second and third papers, ‘ On the Method of Adjust- 
ing the Sizes of the Coloured Images yielded by the Cooke Lens,’ and 
‘ On the Construction of the “ Planar ” Lens, and its uses in low-power 
Photomicrography,’ respectively, were also read by the President, who 
remarked that the optics of photographic lenses had of late years become 
so specialised that they now formed quite a distinct branch of study, to 
which he had given too little attention to be able to follow Mr. Jourdain 
in his account of the Cooke lens. When a subject became specialised, a 
specialised nomenclature grew up with it ; and so rapidly did things 
progress nowadays, that unless one kept oneself au fait with the current 
literature and modes of expression on any particular subject, in a very 
little while one became unable to understand the meanings of the terms 
employed. Therefore, if Mr. Jourdain had been present, he would like 
to have asked him one or two questions with regard to the foci of the 
negative and two positives of which the lens was composed. He was 
sure, however, that the Fellows present would give Mr. Jourdain a 
hearty vote of thanks, both for sending the Cooke lens there, and for 
his remarks upon it, as well as for his interesting notice of the apochro- 
matic objective constructed without fluorite. 
The thanks of the Society were unanimously voted to Mr. Jourdain 
for his communications. 
Dr. J . Tatham inquired if the President had seen one of the apochro- 
matic lenses described as being made without fluorite ? 
The President said that he had not yet had an opportunity of seeing 
one, but he hoped to do so shortly, as Mr. Jourdain had promised to 
send some up for exhibition. 
The President read a note ‘ On the Optics of Photographic Lenses.’ 
The President said that Mr. Bousselet had got together for exhibition 
that evening a most interesting collection of living objects connected 
with pond-life ; he might say that he had never seen a better collection 
