218 Ohject-glasses and their Definition. 



to ask the question, Has anyone ever seen them directly through 

 the microscope as plainly as this ? * 



Again was the immersion lens delineated in the region of fancy 

 and romance, and then, by the apphcation of a few commonplace 

 measurements taken from the real thing, it became known that it 

 had no property for collecting from a baLsam-mounted object a 

 greater number of rays, but that the hmit is the same as in the dry 

 lens. 



" As it seems right in the eyes of some of the old lovers of dry 

 objectives to dispute a number of things that they did not learn in 

 their youth, it may not be out of place to quote a principle at which 

 advanced optical students are quite au fait * * * * It would 

 seem that these writers must be unacquainted with the standard 

 works on optics, and so of course could not be expected to know 

 that the angle of total internal reflexion," &c., &c. 



These have been noticed by others as specimens of good taste and 

 literary courtesy ; I, to whom they were apphed, record them but to 

 forgive them, with the desire that their integrity may rest upon the 

 merits of work past or to come. 



I have carefully examined the aplanatic searcher made under 

 Dr. Pigott's directions, and * * * * but avoiding all expression 

 of disappointment ^at the result, I add my voice to those that take 

 the will for the deed, and exclaim. Let us be thankful ! f 



* I have again to thank Colonel Dr. Woodward for a series of twenty photo- 

 graphs, which are very remarkable specimens of clever manipulation. Ten of tlie 

 Podura are illuminated to obtain the beaded appearance, which is most plainly 

 shown in the scale known under the titles of " Black Podura," " Speckled 

 Podura," Degeeria domestica, Seira domestica, Degeeria nigromacuiata ; but, as I 

 have before remarked, the " beads" are developed at the sacrifice of that sliarp- 

 ness and distinctness of outline associated with the note of exclamation 

 markings. Xo. YIII. is mos-t distinct, in which the ! ! ! a])pear with the 

 " headings," or, rather, corrugations, not on but bet'ceen them. 



t " Great things lor science have been achieved by means of the microscope, 

 but these will now be outdone by the aid of an apparatus which the inventor calls 

 ' An Aplanatic Searcher,' and which, when applied to the microscope, increases 

 its power, its penetration, and capability of definition to an almost incredible 

 degree. Objects, wliich under the best of ordinary microscopes appear as black 

 patches, are seen to be full of beads, or lines, or grooves, or possessed of a fashion 

 of some sort, with the aplanatic searcher. Some theories of vital organization are 

 built on discoveries made by the microscope ; and if these discoveries now prove 

 to be delusions, the theories will have to be abandoned or re-written. This is 

 especially Ibe case with the 'germ theory " and the theory of spontaneous gene- 

 ration. The minute disk ofi jelly in which the germ was supposed to lie is now 

 proved by the aplanatic searcher to be a delusion— a false image — due to nothing 

 more than the imperfection of the object-glass. From this it will be understood 

 that a revolution in microscopical science may be looked for. The inventor of this 

 new and searching apparatus is Dr. Royston-Pigott. A full accdunt thereof will 

 shortly appear in the ' Philosophical Transactions.' Meanwliile, some particulars 

 have already been published in the 'Proceedings of the Eoyal Society.'" — 

 Chamhcrs's Journal, Dec. 31, 1870, 



