PROCEEDINGS OF THE SOCIETY. 595 



had the advantage of reading the paper in MS., he was able to say 

 that it contained a most exhaustive discussion of the subject. 



Mr. Crisp said that it was the first attempt that had been made to 

 establish a definite relation between aperture and power, and amongst 

 other benefits it could not fail to prevent the perpetration in future 

 of such absurdities as had been issued in the way of low-power 

 objectives with very large aperture. 



The Chairman said that the report of the committee appointed 

 to consider the question of standard gauges for eye-pieces and sub- 

 stages bad been adopted by the Council. The gauges recommended for 

 eye-pieces were 1*35 inch and 0*92 inch, and for substages 1*5 inch. 



The following is the report of the committee : — 



" The committee who were appointed under a resolution of the 

 Council directing them to ' consider the advisability of establishing 

 standard gauges for eye-pieces and substages,' after communication 

 with the leading opticians and with Fellows of the Society, now 

 present their report as follows : — 



" The committee have found that a very general desire exists on 

 the part of workers with the Microscope that there should be 

 standard gauges both for eye-pieces and substages, and the com- 

 mittee therefore resolved ' That in the opinion of this committee it is 

 expedient that standard gauges should be established for the eye- 

 pieces and substages of Microscopes.' 



" In considering the question of the number of standards to be 

 adopted, the committee were of opinion that it would not be prac- 

 ticable to establish a single uniform gauge for eye-pieces. On the 

 one hand, a considerable number of Microscopes issued are of small 

 size, and could not with convenience be fitted with a body-tube of 

 large diameter ; while, on the other hand, it would be undesirable to 

 reduce the diameter in use with first-class instruments. The same 

 considerations do not apply to the case of substages, which are 

 frequently of as great a diameter in the smaller instruments as in the 

 larger. The committee, therefore, resolved to recommend ' That the 

 standards for eye-pieces should be two in number, with a single 

 standard for substages.' 



" With regard to the size of the standards, the committee did not 

 feel themselves able to treat the question as one entirely open, but 

 considered that it would be preferable to select some sizes already in 

 general use, so as to involve the minimum of change. They there- 

 fore resolved to recommend ' That the two standard gauges for eye- 

 pieces should be, for the No. 1, 1-35 inch, and for the No. 2, 

 • 92 inch (external diameter), and that the gauge for the substages 

 should be 1*5 inch (internal diameter).' The No. 1 gauge is 

 generally used for the larger instruments in England, whilst No. 2 

 is that adopted by many Continental makers." 



Mr. Crisp said that it should be mentioned that there had been 

 some difference of opinion, both on the part of the committee and 

 the Council, as to whether there should not be a third intermediate 



