558 



NOTE. 



Royal Microscopical Standards for Eye-pieces and Substage. 



The Standards for Eye-pieces adopted by the RM.S. in 1899 * 

 were four in number : — 



No. 1. 0-9175 in. = 23-300 mm. 



No. 2. 1-04 „ = 26-416 „ 



No. 3. 1-27 „ = 32-258 „ 



No. 4. 1-41 „ = 35-814 „ 



The size being the internal diameter of the draw- tube, and the 

 tightness of the fit being left to the manufacturer. 



The standard size for the internal diameter of the Substage- 

 fitting was fixed at 1*527 in.; this size had been used by the 

 English trade for many years, the variation amongst different 

 makers being not more than a few thousandths of an inch. 



A set of Plus; and King Gauges for the above sizes were ob- 

 tained, and these have been kept for reference at the Society s 

 rooniv 



The Council of the Society have now made an arrangement 

 with the Director of the National Physical Laboratory whereby 

 the gauges have been deposited at the National Physical Laboratory, 

 and makers' gauges may be compared with the standards on pay- 

 ment of a small fee. 



At the present time practically only two Eye-piece Standards 

 are in general use, viz. Nos. 1 and 3, and the Council recommend 

 that these should be known respectively as the Small and Large 

 size E.M.S. Standard Eye-pieces.f 



* See Trans, of the Royal Micr. Society, 1900, p. 147. 



t For Specification of Royal Microscopical Society Standard Screw Thread 

 for Objectives, see 1915, p. 230. 



