PROCEEDINGS OF THE SOCIETY. 905 



objective exhibited. It is not merely an objective of tbe usual form 

 in a tapering or conical brass mount, but the front lens is itself a 

 cone." No such objective had ever been seen in America previously 

 to that first made by Tolles in May 1870, and there is no record of 

 any having been made in England or anywhere else. 



Mi*. Ingpen said he was now able to exhibit the objective he 

 referred to at the last meeting by Andrew Ross. Its aperture was 

 60°, and the front lens, which was a triplet ^ inch in diameter, was 

 coned down to an angle of 120°, reducing the front to T x 7 inch surface. 

 Opaque objects could be illuminated at an angle of 30° from the level 

 of the slide. The primary reason for coning this particular objective 

 was the use of a very narrow Lieberkiihn, but objectives were also 

 coned for the purpose of getting rid of "stray light," to which par- 

 ticular attention was afterwards called in an article by Mr. Wenham 

 on angular aperture, published in 1874, after which many lenses 

 were coned for that purpose. The practice had since been to a great 

 extent abandoned, in consequence of the reduction of aperture caused 

 by it. 



Mr. Beck said it was quite preposterous for any one to suggest 

 that there was any novelty whatever about the objective referred to 

 by Mr. Stodder. James Smith, who was a very skilful worker in 

 glass, used to pride himself upon the way in which he was in the 

 habit of coning down object-glasses. He used to fit them in a cell, 

 and then turned them down in a lathe with a diamond, so that the 

 front lens had no cell at all. A small brass cap was fitted over it to 

 prevent any danger of its being injured. 



Dr. Edmunds said that the Fellows always cordially welcomed 

 communications from foreign microscopists. It was true that it had 

 been demonstrated this evening that the idea of coning off the front 

 lens of an objective had been tried long since by English opticians, 

 and therefore that the plan communicated by Mr. Stodder was not 

 new ; but he thought Mr. Tolles was evidently entitled to the merit 

 of an independent invention. These discussions over devices tried 

 and lost sight of, only to be reinvented a generation later, showed the 

 value of the figures and technical descriptions of apparatus which 

 had been published in the Society's Journal of late years. He asked 

 if Mr. Beck or Mr. Ingpen could give the meeting any references to 

 previous descriptions of the method. 



Mr. Beck said it was recorded in the catalogues of their firm ; 

 and if any other evidence was needed, it might be found in the fact 

 that a large number of microscopists were in possession of similar 

 objectives. Mr. Beck then examined the Society's Cabinet, and pro- 

 duced one of James Smith's objectives, made before 1847, the front 

 lens of which was coned off in the manner described, and a small cap 

 put over it. 



Mr. J. Mayall, jun., said he understood Mr. Stodder's claim on 

 behalf of Mr. Tolles to be that he originated the plan of reducing the 

 front lens or lenses of an objective, as near as possible to the cone of 

 light transmitted, so that the exposed surface of the front lens was 

 the exact working diameter required for the aperture of the whole 

 combination. By such acute coning no doubt the greatest range was 



