124 
PROCEEDINGS OF THE SOCIETY. 
three weeks in examining them without coming across some which were 
not only interesting but also new to science. 
The Chairman said the Society were greatly obliged to Mr. Bennett 
for bis very interesting communication, which, like the others which he 
had made, was both practical and useful, showing that it was possible to 
do very good work during holidays. 
Mr. Crisp reminded the Fellows that at the last meeting mention 
was made of a new objective with an aperture of 1 • C3, the price of 
which was said to be 400Z. Some doubt was expressed at the time as ' 
to whether the account was not somewhat exaggerated, but since then 
Mr. Mayall had communicated with Jena, and they had received several 
communications, which enabled them to se2)arate the truth from fiction. 
These conmuinieations were from Prof. Abbe, Dr. Czapski, and Dr. Van 
Heurck, in English, German, and French respectively, and were read to 
the meeting in abstract by Mr. Crisj). 
A series of photomicrographs taken by Dr. Van Heurck with an 
objective of N.A. 1-63 with magnifying powers of 30(J0, 10,000 and 
15,000 diameters was exhibited in illustration of the subject. 
The Chairman said the meeting was greatly indebted to Mr. Crisp 
for the trouble he had taken to j)resent to them in so clear a way what 
it must have been difficult for any one to render into English as he had 
done whilst reading. They were also very glad to see the photograjdis 
which were exhibited in connection with the matter. Those who had 
seen Dr. Zeiss’s jJates in his catalogue and had carefully studied the 
one of P. angulatim, would have noticed that there were six intercostal 
marks shown round each “ cavity.” In the photogra23h before them 
these were all exaggerated, but they were not materially altered in 
appearance, and were aj^parently as real as the cavities themselves. By 
some these appearances have been considered as entirely “ ghostly,” but 
if they were so, he could only say that in these 23hotogra23hs of Dr. Van 
Heurck it had been j^ossible to make them look exceedingly material. 
The double layers had been seen very clearly before by some of their 
own observers, but he did not think they had been seen so well in a 
photograph ; the detail of the intercostal markings was also remarkable. 
No. 4 of the series was marked as being “focused on the hexagons,” 
which he suj)i)Osed to mean focused so as to get that appearance. 
Mr. T. F. Smith said it seemed to him that one material point in the 
descrij)tion had been left out, and that was the aperture of the substage 
condenser, because the truthful nature of what was seen was dependent 
u|)on that. 
Mr. Crisp referred to the description, and said it was mentioned that 
the aperture of the condenser was 1 • 60 N.A. 
Mr. Smith asked if it stated whether the condenser was stopped 
down in any way ? 
Mr. Crisj) said the illumination used was stated to be monochro- 
matic sunlight, “moderately obli(j[ue” with Amphipleura, and “strictly 
axial ” with Pleurosigma. 
Mr. Smith thought that if it was oblique it was calculated to give a 
false image. 
