CHOICE OF OBJECTIVES FOR REGULAR WORK. 209 



objective sometimes read about is simply a myth. Here 

 is another instance where the French proverb fits to a 

 charm. The fundamental error having- been committed, 

 the evil consequences are sure to follow suit. 



Now in the course of a year or two, our correspond- 

 ent having meanwhile obtained some considerable know- 

 ledge of the microscope, and being in a position to 

 make a further investment, he has simply to purchase a 

 first class inch (or two-thirds) of 45, the old inch will 

 still do good service either as a "hack" lens for his 

 rough preliminary work, or it can be made to do yeo- 

 man's duty as a condenser, as has already been referred 

 to. It will, in very fact, be just as much needed as 

 before ; there will be no thought or occasion for its sale 

 or exchange. 



It will probably happen, too, that in a little while 

 the one-fourth will be supplemented by the addition 

 of a one-sixth or one-tenth of high balsam angle. In 

 this case the great advantage derived from the previous 

 use of the one-fourth will at once be made manifest. 

 Our correspondent will be enabled to work the new 

 glass with tolerable satisfaction at sight, improving 

 daily as he continues its use ; and if so be that he can 

 get a few words of instruction from some acknowledged 

 expert, they will be readily understood and appreciated. 

 And here, again, note that the one-fourth does not even 

 now become a superannuated, worn out objective, to be 

 sold at the first chance to the highest bidder. On the 

 other hand, it will continue to be used generally for a 

 considerable time while experience with the last pur- 



