MOUNTING OF MICROSCOPIC OBJECTS. 



devised by myself many years since, in my early microscopical days, 

 and which costs but a fraction more than the simplest turn table 

 without it, has been found so satisfactory in my own work, as well 

 as that of many friends who have adopted it, that I am led to 

 describe it here and to give an illustration as well. Indeed, the 

 latter shows the simple device so well that further description is al- 

 most useless. A sheet of thin brass with a stop at the left hand end, 

 precisely one and a half inches from the centre, is attached to the 

 surface of the whirling table by a small milled head; by which the 

 distance of the edge of the brass plate from the table's centre may 

 be varied more than half an inch. A slide precisely 3x1 inches, 

 having been accurately centered on the table by means of the con- 

 centric rings turned about the centre of the latter, and held in 

 position by the usual spring clips, the guide plate is moved up 

 until the lower left hand corner of the slide rests securely in the 

 angle formed by the upper edge of the guide and the stop at its 

 left; when the milled head is screwed up tight and the centering 

 arrangement is ready to do its allotted work. It follows that any 

 rectangular slide 3x1 inches, slipped under the spring clips and 

 into the angle of the guide, must have its centre exactly over that of 



12. Turn Table. 



the table, and a ring of cement once run upon it when so placed, 

 can be followed by as many more as are desirable, by simply replac- 

 ing the slide in the same angle, without any trouble in adjusting. 

 Since, however, very fe\v slides are absolutely rectangular or have 

 exactly parallel edges, it will be found convenient in practice, to 



J 3- Writing Diamond. 



