104 SUMMARY OF (JURRENT RESEARCHES RELATING TO 



5. Please suggest such a nomenclature whicli seems to you most 

 generally applicable and desirable. 



6. Do you consider it desirable that eye-pieces should be so con- 

 structed — by means of a shoulder or other device on the longer ones — 

 that all should pass the same distance into the tube of the Microscope, 

 thereby preserving the blackening of the inside of the microscope- 

 tube? 



7. Please give inside diameter of microscope-tube, or draw-tube 

 where there is one, or outside diameter of that portion of eye-piece 

 fitting into the microscope-tube for each size of stand made by you. 



8. Do you consider it desirable that two, or three, or more standard 

 diameters of tube for Microscopes be generally adopted with a view to 

 interchangeability of eye-pieces ? 



9. Please suggest the number of sizes and the inside diameter of 

 tube in each case, which you would recommend for adoption. 



10. "Will you adopt a standard set of sizes if agreed upon and 

 recommended by this Society ? 



11. Please give this committee the benefit of any suggestions not 

 included in the above answers." 



The inquiry of the American committee embraces a wider field 

 than that of the Society's committee, which was limited to the ques- 

 tion of standard gauges for eye-pieces and substages, and does not 

 include a consideration of the proper denomination for eye-pieces, 

 though the present system of nomenclature is an even greater evil 

 than that of the numerous different sizes. 



Every one feels the inconvenience of the Continental method of 

 numbering or lettering chjectives, a special table being necessary to 

 enable the relative powers of Monsieur A's No. 2, and Herr B's 

 No. 3 to be compared ; the English plan of denoting the objective 

 by inches and fractions of an inch is obviously preferable. 



Having adopted this improvement, however, and even being accus- 

 tomed to wonder how our Continental brethren can still tolerate so 

 barbarous a system of marking objectives, it is remarkable that 

 the designation of eye-pieces should have been allowed to remain 

 on the princij^le abandoned for objectives, and that the letters A, B, 

 C, D, &c., by which they are known, should still express absolutely 

 nothing as to their magnifying power, beyond the fact that D is to 

 some undefined extent more powerful than C, C than B, and B than A ; 

 so that not only is it impossible to compare the eye-pieces of dif- 

 ferent makers, but it is not possible to do so in the case of the same 

 maker, unless the powers are actually known. 



If eye-pieces were, however, denoted on the same principle as 

 objectives, nothing whatever would be lost, and much would be 

 gained. 



For instance, if the magnifying power of a i-inch objective with 

 a C eye-piece is required, it will be 500 or 750, according as the eye- 

 piece is that of one or the other maker. If, however, instead of 

 being labelled C (or No. 3), the eye-pieces were called |-inch or 

 1-inch, the necessary calculation (50 x 15 = 750 or 50 x 10 = 500) 

 is instantly made. 



