PROCEEDINGS OF THE SOCIETY. 173 



Mr. H. L. Brevoort's letter was read, asking for references to 

 papers, &c., on the subject of the construction of fur fibres as distin- 

 guished from hair. " There is," he said, " a large field of practical 

 usefulness open to any one who may acquire a fuller knowledge of the 

 construction of and method by which fur fibres operate upon one 

 another in the practical operation of forming felt goods." 



Mr. Crisp said he could not call to mind any paper which had been 

 published in which any distinction between hair and fur had been 

 drawn, at any rate not scientifically. 



Mr. J. Beck thought none had been, in fact, made, and that the 

 distinction was merely a commercial one. 



Mr. H. G. Hanks' letter was read as follows : — " I send a package 

 for distribution to Fellows specially interested containing diatoma- 

 ceous earth thrown up by the waves at Santa Monica, and deposited in 

 the sea-beach debris, like the celebrated fragment found in March 

 1876. It has been examined by Mr. Wm. Ashburner, of the San 

 Francisco Microscopical Society, and found to resemble the true Santa 

 Monica, although not so rich." 



Mr. Crisp called attention to Dr. Van Heurck's donation of two 

 photo-negatives of Amphipleiira pellucida, and six slides in which the 

 diatoms had been burnt on the glass and silvered. 



Mr. J. Mayall, jun., said that Dr. Van Heurck had sent two sets 

 of slides for the Society's collection ; one set of which had been pre- 

 pared by Dr. A. Y. Moore's process and one by a new process devised 

 by Dr. Van Heurck. In the former process there was a tendency for 

 the silvering solution to get under the diatoms, and to obviate this 

 Dr. Van Heurck put them into a muffle and heated them until the glass 

 softened, and the diatoms became partially imbedded in it. The fol- 

 lowing translation of the letter which accompanied the photographs 

 was then read : — 



" I have the honour to submit to the Society a new photograph of 

 the ' beads ' of A. pellucida. 



This new print exhibits the double striation well defined on a 

 portion of the valve. I think it will be very difficult to resolve a 

 larger portion in consequence of the special kind of illumination, 

 which does not cover the whole valve at once. 



The photograph was obtained by using a rigid stage, in order to 

 obviate the flexure which I found to be a serious drawback in 

 mechanical stages. The success I have had convinces me that my 

 former less perfect results were principally defective through the use 

 of a mechanical stage. 



I must also add that I have recently found that it is necessary to 

 give a longer exposure to the photographic negative than I formerly 

 gave, for with such preparations and with this kind of illumination 

 (the vertical illuminator) we cannot distinguish the ' beads ' unless 

 the diatoms appear green in the field of the Microscope. It is well 

 known that this colour is unfavourably actinic for the development of 



