1884.] 



MICROSCOPICAL JOURNAL. 



93 



worse in manipulation than ourselves. 

 Our assertions concerning this ce- 

 ment* have been flatly contradicted, 

 but, as it seems, without sufficient 

 regard to experience and facts. The 

 reader will do well to fix his faith 

 upon shellac, and use the white zinc 

 outside only. 



A black finish is best given with 

 asphalt. We prefer to round out the 

 cells with the asphalt and gold-size 

 mixture, letting one or two coats run 

 up over the edge of the cover-glass, 

 and then finish with asphalt alone. 

 The reason for this is that the mixed 

 cement is more elastic than the as- 

 phalt alone, and will hold the cover 

 more securely. 



A method of finishing that is to be 

 highly recommended has been long 

 used by Mr. C. F. Cox, and his 

 mounts present a very attractive ap- 

 pearance. He uses what is known 

 in color shops as Munich lake, which 

 is sold in collapsible tubes. 



Motinting in Cement or Ring 

 Cells. — Deep cells may be made 

 either by cementing curtain-rings to 

 the slide by means of shellac, marine 

 glue, or other mixture, or by building 

 up cells with some cement or ground 

 pigment in oil. When using the 

 curtain-rings they may be flattened 

 by pressure, as described by Mr. 

 Durkee in another column, or even 

 with a hammer, in case they should 

 be too deep, and this has the advan- 

 tage of giving them a greater surface 

 to adhere by. The reader will find 

 numerous methods of making opaque 

 cells by looking over back volumes 

 of this Journal. 



To build up cells of cement or 

 ground pigment the best method is 

 to take up a considerable quantity on 

 a small brush and spread it on the 

 middle of the slide on the turn-table. 

 Then with the pen-knife turn up the 

 cement in a ridge to form the cell of 

 the proper size and depth. For such 

 cells we advise the use of thick, plain 

 shellac, but if it is desired to make a 



♦ See page 30. 



more ornamental ring the shellac 

 may be thickened with vermilion. 

 The greatest care should be taken 

 that such cells are thoroughly hard 

 before they are used. 



To mount in such cells the bottoms 

 should be covered with black paper, 

 or by one of the dead-black mixtures 

 mentioned on page 74. The cover 

 should be cemented on with shellac, 

 and the finishing done precisely as 

 described for the wax cells. 



We have already mentioned the 

 use of gum water to attach objects to 

 the slides or to the backgrounds of 

 cells. A superior liquid for this 

 purpose was mentioned in one of the 

 preceding volumes of the Journal, 

 but we give a more full account of 

 its preparation in this place. It is a 

 solution of arabin or purified gum 

 arabic, the use of which was sug- 

 gested some time ago by Mr. H. J. 

 Waddington, who describes the me- 

 thod of preparing and using it* as fol- 

 lows : — 



' To obtain arabin for microscopical 

 use, ginn Arabic should be selected as 

 clear and white as possible. This is 

 to be dissolved in distilled water to 

 the consistence of thin mucilage. It 

 should then be filtered, and the filtrate 

 poured into rectified alcohol and well 

 shaken. The arabin immediately sep- 

 arates as a white pasty mass, and the 

 whole becomes semi-solid. It must 

 be placed on filter-paper, and washed 

 with alcohol until the washings are 

 perfectly free from water, and the al- 

 cohol comes oft' as pure as it went on. 

 The arabin may now be allawed to 

 dry spontaneously. The edges of the 

 surface of the mass will probably be 

 found to be viscid, owing to the ab- 

 sorption of water from the atmosphere 

 or from the alcohol — but the I'emain- 

 der will be a perfectly pm-e white pow- 

 der. This should be shaken oft' the 

 filter and preserved. 



'Like ordinary mucilage, it is very 

 liable to become mouldy if kept in so- 

 lution, but when once dry on a slip 



* Journ. ^iiekett Club. 



