226 Optical Curiosities of Literature. 



why. It was not perhaps to be much wondered at that an amateur 

 worker should himself have made a mistake like this, or even that 

 he should assert it in such a self-complacent tone. The unaccount- 

 able thing is that he should have passed over the startling discre- 

 pancy between his own doctrine and the professions of the makers he 

 was eulogizing. For in the hsts of Merz, Hartnach, and Gundlach, 

 with all of which he is on familiar terms, the immersion apertures 

 are given rising by degrees to 175^. But whatever may have been 

 the origin or account of his error, Mr. Mayall has himself preserved 

 ever after a judicious and most commendable reticence, following in 

 this the well-known wisdom of the " leading journal," which, once 

 committed to a misstatement, neither withdraws nor explains, leaving 

 its readers to explain it for themselves as best they can. 



But the choicest of the flowers by many degrees is that which 

 was presented by Mr. Tolles, of Boston. The episode is too recent 

 to have been forgotten, but, the discussion being ended, it may be 

 regarded as now in some sort appertaining to history. It was on 

 this wise. The original controversy about angular aperture having 

 Bome time before come to a close, Mr. Tolles who, unknown to 

 everyone, had been studying it, appears unexpectedly wich a con- 

 tribution which seemed to open up an entirely new phase in the 

 question. Putting theory aside, he simply tests the fact by an 

 experiment. And he finds that the disjmted aperture can exceed 

 the famous 82^, because in fact it does exceed it, being 110°. This 

 certainly seemed starthng, for facts are proverbially hard things to 

 reason against, and Mr. Tolles, a practical worker, might be sup- 

 posed to know a fact when he saw it. It appeared, however, that 

 this was just what he did not know. Mr. Wenham instantly pointed 

 out the fallacy; he had made a mistake in arranging the saddles for 

 his horses, or, not to use metaphor, had measured the wrong ray. 



So far the oversight was not unnatural, although one which a 

 " professional " might have been expected to look at twice before 

 committing his reputation by printing it. But a greater thing was 

 coming. Having again reflected for some time, Mr. Tolles again 

 appears, and this time also on a new ground. The experimental line 

 having been found not to work, he now elects to win with Theory. 

 Cementing to the front of his object-glass an imaginary hemisphere 

 to match it, he forms an imaginary sphere, and then proceeds to 

 reason upon it. As thus : — The rays can pass into this sphere below, 

 and out of it above at every angle. And there is no difference if the 

 hemispheres are connected, not immediately, but with the slide and 

 immersion water between them. As before, the rays will pass in 

 and pass out at every angle, and so the aperture has no limits 

 at all. 



This is the flower I have spoken of as being, all things consi- 

 dered, the most remarkable yet seen. You cannot, says the proverb, 



