PROCEEDINGS OP THE SOCIETY. 
271 
Mr. Mayall said the new objective would naturally bo regarded by 
the Society with extreme interest. In order that its merits might be 
tested, the Council had recommended that Dr. Dallinger, Mr. Nelson, 
and himself, should form a committee for the purpose of examining it, 
and reporting the result at their next meeting. Prof. Abbe had for- 
warded with the objective a condenser, of 1*6 N.A., and a flint-glass 
slide, containing mixed diatoms mounted by Dr. Van Heurck, of Antwerjn 
It was, of course, understood that in order to exhibit the full power of 
the increased aperture, it was necessary to employ a condenser of corre- 
sponding aperture, and the objects to be viewed must be mounted on 
slips, with covers, and mounting and immersion fluids of corresponding 
high refractive power. 
Mr. C. L. Curties said that Prof. Abbe had also sent for the Society’s 
acceptance a supply of flint-glass slips and cover-glasses for use in 
mounting objects for examination with the new objective. 
The Chairman was sure that the thanks of the Society would be 
given to Prof. Abbe for his valuable and interesting donation, and that 
the Society would be very much interested in hearing the report of the 
gentlemen who had undertaken to examine it. 
Mr. Mayall called attention to two Microscopes exhibited by Mr. 
Crisp. One of these was an example of the highest grade of construction 
made by M. Nachet ; a special novelty about it was that the stage was 
fitted with two small mirrors, one concave and one plane, which were 
placed right and left of the stage, so that an observer looking down the 
body-tube with one eye could see in the plane mirror with the other eye 
the image of the profile of the objective, and could thus see when the 
objective was approaching dangerously close to the cover-glass, an advan- 
tage which he was himself hardly able to appreciate. He thought 
appliances of that kind interfered with the freedom of manipulation. 
The general construction should be compared with that of other opti- 
cians in France, and then it would probably be found to rank high, for 
centering movements were applied to the substage, which had also a fine- 
adjustment. There seemed to have been an oversight in the fitting of 
the rackwork of the coarse-adjustment, because when run down low with 
the pinion, the body-tube was apt to slip away from the pinion and crush 
down upon the stage. 
Mr. Crisp said this defect had been noticed by himself, and he had 
also found, in handling the stand with average care, the body-tube rack 
ran so unusually free that the lower part of the instrument had narrowly 
escaped dropping on the floor in the removal from one table to another. 
Mr. Mayall said that the other Microscope exhibited by Mr. Crisp 
was constructed by M. Pellin, of Paris, successor to the late Jules 
Duboscq, for the purpose of examining and photographing adulterations 
in food, which was one of the official duties at the Paris Municipal 
Laboratory. It stood upon a wide tripod provided with levelling screw's, 
which were probably of use in examining fluids. The photographic 
accessories were of substantial construction, consisting of a brass shaped 
tube, the smaller end fitting as a socket over a cylindrical chamber 
encircling the eye-piece, and the upper end receiving the sensitive-plate 
holder at about twenty inches from the objective. 
