1890.] MICKOSCOPICAL JOUENAL. 3 



A New Form of Mounting Clip.* 



By G. H, BRYAN. 



There are, I suppose, few microscopists who have not tried the 

 use of various forms of spring clips for mounting in Canada balsam, 

 and who have abandoned them because they do more harm than good. 

 The pressure produced by the ordinary clip being far from uniform, 

 some mounters have invented spring-clip boards or arrangements in 

 which the pressure is produced by weight. But all of these possess 

 this disadvantage, that delicate objects are ruined by the pressure, 

 while those that are more elastic will lift the cover up as soon as the 

 pressure is removed, thereby admitting air. In order to keep the cover 

 in position while the balsam is " setting" without producing pressure, 

 I devised, early in 1SS7, the clips shown in the frontispiece, figure 4, 

 to which I give the name of '^ Pressureless Edge Clips." Their use 

 will be obvious from the figure. Two are required for each slide, and 

 their points are brought to bear against the edge, not on the top of the 

 cover, which is thus held fixed. They are made of brass wire, of dif- 

 ferent sizes according to the size of the cover ; the form marked a is es- 

 pecially useful for thick objects. When applied to newly-mounted 

 balsam slides, a great deal of the superfluous balsam may be scraped 

 from round the edges without shifting the cover, and the slide then 

 " baked " on a hot water cistern or elsewhere for a week or more, and 

 there being no pressure, there is no danger of " springing" when the 

 clips are removed. I now find the clips invaluable, and several friends 

 have also adopted them. 



Use of Eye-Piece Micrometers and other Eye-Piece Accessories. 



By E. J. JONES, 



VICE-PRESIDENT OF THE CALCUTTA MICROSCOPICAL SOCIETY. 



The eye-piece micrometer is more generally applicable in measuring 

 than the stage micrometer, for while the latter can be used directly only 

 with very low powers, the former can be directly used in all cases. The 

 stage micrometer can, by the help of the camera lucida, be used indi- 

 rectly for measuring even with high powers. 



There are several forms of this micrometer. The simplest consists 

 of a glass disc cut so as to fit into the eye-piece, resting on the dia- 

 phragm, at the focus of the upper glass of the eye-piece. On this glass 

 there are ruled two series of fine lines at right angles to each other, and 

 at equal distances, so as to form squares. It is quite immaterial what 

 the distance between the lines is, so long as they are all equal, and 

 not too wide apart. The most convenient distance is from 1-25"- 

 i-ioo", though the closer they are together the more chance there is 

 of the lines nearly or quite coinciding with the edges of the objects to 

 be measured ; less error is thus introduced in the computation of the 

 fractions of an interval. In order to use this micrometer, it is neces- 

 sary to obtain an accurately divided stage micrometer, with which 



*Science Gossip, December, 1889, P- 271. 



