192 H. T. WHITTELL ON MOUNTING IN GLYCERINE. 



and then some of them have given me a valued slide, but until 

 lately I have not found any plan upon which I could rely with the 

 same certainty as when mounting in a ring. Perhaps the best re- 

 sults have been obtained from passing a layer of very thick 

 mucilage along the edges of the cover. This mixes with the 

 glycerine, and, in dry weather (like the summer in Australia), the 

 whole sets with sufficient firmness to receive coatings of a more 

 durable cement. Coaguline applied warm has also given me fair 

 results — say in half the cases tried. The difficulty with both these 

 fluids is, that they retain some quantity of water after setting, and 

 this is apt to cause the covering cements to peel off. I have lately 

 obtained much more satisfactory results, by a simple process which 

 I venture to ask the Club to assist in testing. 



As much glycerine as possible is first removed from the slide by 

 the usual plan of wiping, and absorbing with bibulous paper round 

 the edges of the cover. A little gold size — that sold to artists is 

 best — is rubbed up with a little whiting that has been previously 

 well dried in an oven, and this is poured into a bottle for use. 

 Some of the whiting settles to the bottom, but a quantity is held in 

 suspension, and a larger proportion can always be obtained by 

 shaking up the bottle. By means of a fine brush a little of this 

 chalk cement is passed along the edges, and just outside the cover- 

 glass, taking care to fill up the angle between the slide and cover. 

 To prevent moving the preparation, it is better in this stage to 

 imitate, what the artists call " stippling," than to take the brush 

 along in one sweep. The cement falls from the brush as one pro- 

 ceeds, and it is easy to see when enough has been applied. In my 

 own practice, while taking care to have sufficient cement to fill up 

 the angles, I aim at having as narrow a line as possible around the 

 edges of the preparation. The slide is now set aside for twelve or 

 twenty-four hours, when the layer of cement will have become 

 tough, and will be found to hold the cover effectively in its place. 

 The slide is now put into water to wash off all trace of glycerine, 

 and is afterwards set on end to drain and dry. A ring of gold size 

 or other cement may afterwards be applied in successive layers, and 

 in due time, when all is firmly set, a finishing layer of white cement 

 or of asphalt may be applied. 



I have now many slides prepared as described, and I seldom fail 

 to preserve anything I wish. As an illustration, I may mention a 

 rather severe test in which the plan answered admirably. I had 



