222 



A few remarks were made by Mr. Burr and Mr. Ingpen upon Mr. Webb's 

 paper, but they were merely of a technical chavacler. 



Mr. T. C. White presented a beautifully mounted slide of Spliceraplddes of 

 Echino-cactus, and stated that they were easily obtained by rubbing two pieces 

 of the dry stem together, when the raphides fell out in great numljers, mixed 

 with woody fibre. When cleaned and mounted in balsam the}' polarized 

 beautifully, but he thought they looked best as opaque objects. 



The thanks of the Club were voted to Mr. White for his donation. 



Mr, Ingpen made some observations upon the construction and use of the 

 Achromatic Prism. Quoting Quekett's treatise on the Microscope, he stated 

 that the concave mirror was first used by Culpepper in 1750, and seemed to 

 have sufficed for all purposes till in 1840 Dujardin employed the right-angled 

 prism with flat sides in conjunction with his " eclairage" or achromatic 

 condenser. Sir David Brewster had recommended a hemispherical lens, using 

 the flat side as a reflector, but this did not appear to have been much 

 employed. Amici's prism consisted, in efi"ect, of two plano-convex lenses with a 

 prism between them to change the direction of the pencil of rays. This was not 

 achromatic, but Mr. Abrahams constructed a right-angled prism of flint glass, 

 having one of its small faces hollowed out to receive a double convex lens of 

 crown glass, which was cemented to it with Canada balsam, and thus rendered 

 it achromatic. This was the form employed by Messrs. Powell and Lealand for 

 their small prisms for oblique light. In another form, which was shewn to the 

 meeting, a plano-concave lens of flint glass was cemented to one of the convex 

 sides of an Amici prism, and this was probably somewhat superior to the other. 

 This prism was mounted and used exactly like the mirror — the focus for parallel 

 rays was 3^ inches from the side nearest the object, and the light was very 

 pure ;more so, he thought, than that of the mirror, and Mr. Quekett seemed to 

 have held the same opinion. By altering the position of the prism it could be 

 used for very oblique light, or to transmit parallel rays for the spot lens or 

 paraboloid. He considered that the achromatic prism was hardly as well known, 

 or as much used as it deserved to be. 



The thanks of the Club were voted to Mr. Ingpen. 



The President announced that the South London Microscopical and Natural 

 History Club intended to hold a Soiree on or about November 20, at the 

 Crystal Palace, and invited the co-operation of members of the Quekett Club 

 on that occasion . 



Mr. T. C. White asked for information respecting two slides of Ci/iiips which 

 he exhibited. Some time ago he gathered some oak galls, and having put them 

 into a bottle, waited for the insects to hatch out. Owing perhaps to the mild- 

 ness of the temperature some of them had done so. He dissected one of them 

 with the idea of obtaining the rectal papillae, but instead of doing so he got out 

 another very extraordinary afi"air instead. He took after this a gall which, he 

 thought, was rotten, but which, on opening, he found to contain an insect, and 

 on dissecting it he found what he thought were ovisacs, but Mr. Lowne, who had 

 seen them, was of opinion they were not. Mr. White then drew upon the board 

 some sketches of the objects to which he had alluded, and gave some further 

 particulars respecting them, concluding with a wish that Mr. Lowne would 

 state his opinion as to what they were to the meeting. 



Mr. Lowne said that he did not know whether he should be justified in say- 

 ing much about these bodies, having only had a cursory glance at them ; he 

 thought, however, that he might be able to throw a little light upon the 



