166 J. RHEINBERG ON ABBE AND MICROSCOPE THEORY IN GERMANY. 



in which the classical experiments with the Abbe diffraction- 

 plate, or the examination of the objective by means of the Abbe 

 test-plate and of the apertometer, are demonstrated, is even 

 nowadays of rare occurrence. And yet practical microscopy must 

 take heed of these things in many cases, if it does not wish to 

 expose itself to the just reproach of carelessness. The old dictum 

 which N. Pringsheim appended to his dissertation in the year 

 1848 — " Microscopium observatorem non fallit" — has still to-day 

 only too many advocates, towards whom, of course, the indulgence 

 accorded to acting in good faith can mostly be unhesitatingly 

 extended. If the publication of Abbe's treatises on the theory 

 of the microscope only in some measure produces a change, even 

 on this score, one of the aims which prompted the publication of 

 the collection will, at any rate, be fulfilled. 



Joarn. Quekett Microscopical Club, Ser. 2, Vol. IX., So. LG, April 1905. 



