PROCEEDINGS OF THE SOCIETY. 
487 
only difficulty being that the diaphragm came in the way ; this, however, 
was got over, and the objective-box now went easily into the draw-tube 
and left room for the eye-piece. He thought that portability could 
hardly be carried further than it had been in this small Microscope. 
The thanks of the Society were given to Lt.-Col. Siddons for his 
exhibit. 
Mr. Conrad Beck gave a resume of the report of the subcommittee 
appointed to consider the subject of the standard screw for objectives 
(see ante , p. 389). 
Mr. J. E. Ingpen referred to the great inconvenience formerly ex- 
perienced owing to the objectives of the principal opticians not being 
really interchangeable. This seemed to have been caused by slight 
variations in the gauges supplied, and by the different interpretations 
put upon the original instructions by various makers. He had always 
considered Messrs. Powell and Lealand’s as the most normal size ; while 
he well remembered that Messrs. Smith and Beck’s was closer, and Messrs. 
Ross and Mr. Baker’s fuller and wider, so that objectives by the last-named 
makers would not fit the nose-pieces of the first. There was a similar 
difference in the gauges originally employed by Herr Zeiss. Another 
variation was caused by the differences in the diameters adopted for the 
“ shoulder ” or plain part above the screw. Of late years most opticians 
had, to some extent, obviated these difficulties by slight hand-alterations, 
but it was a matter of congratulation that they were not likely to occur 
in the future.* 
The Chairman said they were very much obliged to Mr. Beck for the 
manner in which he had brought the matter before the meeting. The 
difficulty was one which had troubled most persons, and certainly was 
one which he had himself frequently experienced, rendering it necessary 
to get adapters made for particular objectives, and when these were 
procured it often happened that the centering was not so exact as could 
have been wished. 
Prof. Bell regretted to have to say that the Journal was again not 
ready to its time. It was, not, however, on this occasion so much the 
fault of the editor as of one of the contributors who lived in Switzerland ; 
this had occasioned considerable delay in revising the proofs ; he hoped, 
however, that it would hot be more than a few days late. 
He also wished to mention that the Council had not yet fixed the date 
for closing the rooms of the Society, but it was probable that this would 
take place somewhat earlier than usual, as their Assistant-Secretary was 
just now considerably out of health and it was desirable that he should 
be released from his attendance as early as could be arranged. 
The next ordinary meeting of the Society would take place on 
October 21st. 
* Mr. T. Curties reminds me that the first sets of Whitworth’s gauges were 
passed as satisfactory, but that subsequent supplies differed in some degree from 
the originals, and caused much trouble to opticians. As early as 1859, the late 
Mr. Brooke (Trans. Micr. Soc., N.S., vol. vii. p. 95) showed how the “three courses” 
that could be adopted would affect the fitting. — J. E. I. 
