72 THE AMERICAN MONTHLY [Mch 



gauges of all the above sizes be kept in the Society's 

 rooms ; also that the public, on payment of a small fee 

 be allowed to inspect them. The size of the sub-stage is 

 that now in fairly general use amongst English makers, 

 the variations being not more than a few thousands of an 

 inch. The sizes of the eye-pieces are arrived at as fol- 

 lows : — No. 1 is the Continental gauge ; it is in general 

 use on the Continent, and has been adopted by several of 

 the English makers for their students' size instrument. 

 No. 2 is the mean of the sizes used by the English trade 

 for students' and small microscopes, and is apparently 

 meant to meet the objections of those makers who have 

 hitherto clung tenaciously to their own originally adopt- 

 ed sizes. No. 3 is the mean of the sizes used for medium- 

 sized binoculars and other microscopes of a similar class, 

 and is apparently also an attempt to meet the objections 

 of those makers who have hitherto declined or been un- 

 able to adopt the Society's standard. The standard adopt- 

 ed by the Society for this eye-piece was formerly 1-35 

 inches, and therefore those makers who fell into line and 

 adopted this size will now have to alter everything — 

 which seems to us a somewhat ungrateful return for their 

 loyalty, and likely to inconvenience equally those who 

 already possess microscopes made to the old standards. 

 Size No. 4 is, we think, that adopted by Messrs. Powell 

 & Lealand alone, and is not likely to become general, as 

 it is too large for most instruments. We cannot help 

 thinking that two standard sizes only would have been 

 better — the Continental size for students' instruments.and 

 No. 3 size for large instruments. However,we are grate- 

 ful for any advance in the direction of uniformity, and 

 earnestly trust that all our leading makers will now adopt 

 these standards. Buyers of microscopes could materially 

 assist by insisting on their microscopes being made in ac- 

 cordance with the Society's standards. We may add that 

 the standardization of the eye-piece, will follow shortly. 



