there are fixed dimensions, there is on this account a 

 diversity in the products of different makers ; hence it 

 often happens that the objectives of one maker will not 

 fit the stands of others. The writer in 1884 read a 

 paper on this subject before the American Micro- 

 scopical Society and as a result a committee was 

 appointed to bring about a better state of affairs. It 

 failed, however, in obtaining the co-operation of the 

 Royal Microscopical Society, the main reason being 

 the expense involved, so that we must continue to 

 suffer until some concerted action is taken by the 

 manufacturers themselves, which we trust will not be 

 far distant. 



Revolving Nose-Pieces. Changing one objective 

 for another to obtain a different power is time consum- 

 ing and inconvenient; besides, 

 there is danger of dropping 

 the objective and thus a 

 liability of injuring it or dis- 

 turbing or destroying the 

 Fig - 29< object. To avoid this the 



double, the triple, and quadruple nose-pieces are offered, 

 to the first of which two, to the next three, and to 

 the quadruple four objectives may be attached in 

 such a manner that, when fixed to the nose-piece of 

 the microscope, each objective may in turn be brought 

 into use by rotating the nose-piece. Each objective 



43 



