188 



The Se(;retaiiy laid on tho tabic sixty specimens of sound- 

 ings, which had been freed from the tallow *' arming" in 

 two evenings after business hours, at Mr. Dale's laboratory, 

 by Mr. Dale, Mr. Dancer, and himself, assisted by Mr- 

 liichard Dale. The system adopted is that described in Mr. 

 Moslcy's Paper, read to this Section on 21st January, 1861, 

 publislied in the Quarterly Journal of Microscopical Science, 

 vol. 1st, new series, p. 14-3, and is found to answer better than 

 any other method yet made known. 



Professor Williamson presented fourteen specimens of 

 dredgings, supposed to be from the mouths of the Ganges. 



A communication from Mr. A. G. Latham was read, upon 

 the subject named for the evening's discussion, " On the 

 cause of ihe metallic lustre on the wings of the Lepidoptera, 

 both diurnal and nocturnal. 



Mr. Latham believes that the metallic lustre may be 

 simply referred to the pres(!nce of a pigment in the substance 

 of the wing, in some cases light-absorbing, and in others light- 

 reflecting ; all the scales seem equally adapted for reflecting 

 the prismatic colours, consisting of three distinct membranous 

 films, covered with minute irregularities. Mr. Latham sent 

 to be exhibited a number of slides for illustration. 



A communication was read from Mr. Dancer, in which he 

 referred to a paper, read by Sir D. Ikewster at the last 

 meeting of the British Association, containing the following 

 remarks by Professor Dove : — 



" In every case where a surface appeared lustrous there was 

 " always a transparent, or transparent reflecting stratum of 

 "much intensity, through which we see another body; it is 

 " therefore externally reflected light in combination with 

 " internally reflected or dispersed light, whose combined action 

 " produced the idea of lustre. * * This effect we see 

 " produced when many watch glasses are placed in a heap, or 



