47G Proceedings of Learned Societies. 



venience to those in the vicinity. The carbon points lasted for 

 several hours, affording a light practically uniform ; and when they 

 were nearly worn out, a fresh lamp, moving on rails provided for 

 the purpose, was slid into the place of that which was exhausted. 

 In taking its position, it lit of itself: and the displacement of 

 its predecessor caused the worn out points to be extinguished, the 

 change taking place so quietly, and so rapidly, that no interruption 

 of the light was perceptible. A single additional lamp is sufficient 

 to change the fifteen at the proper times, the points being so 

 arranged as to become exhausted in succession. 



New Mode of Dissolving Vegetable Fibre. — Various solvents 

 for dissolving vegetable fibre are known ; but, besides being most 

 unusually expensive, some of them give rise to explosive compounds. 

 It is found, however, that it is readily dissolved by a strong solu- 

 tion of ammoniated copper. Filtering paper, probably on account 

 of the processes employed in its manufacture, dissolves easily, and 

 without residue, in the cupreous solution. The vegetable fibre is 

 thrown down from the solution thus obtained, as a gelatinous pre- 

 cipitate, by boiling, exposure to the air, or the addition of an acid. 

 The ammoniated sulphate will take up so much of the filtering 

 paper as to form a viscid adhesive mass. 



PROCEEDINGS OF LEARNED SOCIETIES .* 



ROYAL MICROSCOPICAL SOCIETY.— June 12. 

 Dr. Arthur Farr, F.R.S., V.P.R.M.S., in the Chair. 



Dr. Carpenter, F.R.S., gave an interesting account of a bino- 

 cular microscope by Nachet, which, though less optically perfect 

 than Mr. Wen ham's, enabled the cone of rays ordinarily passing to 

 the right eye to be transferred to the left, and the left cone to the 

 right, by pulling out a slide containing the prisms. The effect of 

 this is to convert the instrument into a pseudoscope, and to make 

 elevations look like depressions, and vice versa. Dr. Carpenter gave 

 many important illustrations of the principles of stereoscopic vision, 

 and said that to obtain true appearances the angle of aperture of 

 objectives must be moderate in proportion to' their focal length. 

 For a half-inch objective he found 40° gave excellent results, and this 

 corresponded very closely with theoretical calculations. 



He likewise described a dissecting binocular microscope by 

 Nachet, which he praised highly. The larger instrument ha4 an 

 excellent and very simple mechanical stage — a rotat ing movement, 

 something like Smith and Beck's " Popular," and other motions made 

 by the hand, and regulated by spring attachments of a glass object- 

 carrier to a glass stage. 



Professor Rymer Jones described the wonderful changes that 

 occur in the larvae of the Corethra plumicorhis, which he illustrated 



* The most important subject that hns lately come before the Royal Society 

 will be found in the article on die " Recent Discoveries of Mr. Graham." 



