C. 8. ROLFE ON MICROSCOPICAL TURN-TABLES. 249 



in the " English Mechanic." This, I find, is in Vol. xxi., page 69, 

 but, on reference to it, I find that the designer, Mr. C. F. Cox, of 

 New York, had adopted one of the plans which I had discarded, as 

 I am strongly opposed to holding a material like glass in a rigid 

 grip. Either it is not held securely, or there is great chance of 

 chipping it. At the same time I cannot but state that Mr. Cox's 

 arrangement may possess advantages which mine has not. 



The form which I have described entirely satisfied me for a time 

 but I was desirous that the satisfaction I felt should not be confined 

 to myself. I accordingly set about improving away my improvements, 

 and the result has been the turntable shown in Fig. 2, and to this 

 I want more especially to direct your attention, as the arrangement 

 possesses the great advantage of being easily applied to any ordinary 

 turn-table. Moreover the cost of the former one was great, whilst 

 of this, it is but slightly in excess of those at present in use. The 

 figure is a view of the upper side. The top A is by preference made 

 rather larger and heavier than usual, and towards one edge are fixed 

 stops, shown at B B. Opposite to them is a catch C, having a 

 notch in it for the corner of the slide to fit into, the opposite corner 

 at the same time resting against the stops ; this catch can be drawn 

 back by the finger, but is constantly drawn towards the centre by a 

 spring D on the underside. By this means the slide is firmly held, 

 not quite centrally, for the reason previously explained, and it can at 

 any time be replaced exactly in the same position. Springs are 

 also provided for holding those slides which have not been ringed on 

 the table, and for exceptional sizes, and which could not be correctly 

 held by the clipping arrangement. The support for the hand has 

 been made to slide back, this being found of great use when dealing 

 with large or deep cells, but in place of the arrangement adopted in 

 the one shown, it would be preferable to have a " dovetailed" slip 

 on the underside of the top of the rest, sliding in corresponding 

 openings cut out of the supports. I think it but just to add that I 

 have never worked with Dr. Matthews' table. 



