POSITION OF OBSERVE!*. 259 



tuition. The remark is often of late made, "what does 

 all this talk about the handling " of objectives mean? 

 Are we to understand that the real work of the micro- 

 scopist consists in the resolution of a few diatoms, or 

 the exhibition of the rulings of the l9thNobert band? 

 To this we reply, that all this is implied and a very 

 great deal more ; it means that the microscopist shall 

 know as much of the microscope as it is expected of 

 the engineer to know of his level or transit. In 

 geodesy the value of entire systems of costly triangu- 

 lations are wholly dependent on the accuracy of the 

 original base line, and. in a similar manner is the work 

 of the microscopist affected. We often hear old ob- 

 servers claim that all work worth having with the 

 microscope is accomplished with amplifications less than 

 300 diameters ; and then again the scientific contribu- 

 tions resulting from the use of the finest English objec- 

 tives in the hands of physicists like Professors Tyndall 

 and Huxley dependent on amplifications of 5,000 and 

 6,000 diameters, have been seriously called in question, 

 yea, disputed by those working with objectives not 

 worth the weight of their brass mountings! We 

 repeat, that it is eminently the business of the would- 

 be microscopist to know all that can be known of his 

 instrument; if, when he has to an acceptable extent ac- 

 quired this knowledge, if so be that he prefers not to 

 devote his time and microscope to investigation, he has 

 the satisfaction of being conscious that what was done 

 was well done. Had the engineers employed in meas- 

 uring the original base on which the coast survey was 



