222 THE MICROSCOPE. 



gold size has become dry and the slide cleaned off, it 

 may be coloured by aniline mixed in a little cement, 

 or by a coating of water- colour, over which a final 

 thin coating of gold size should be applied. 



A good ringing medium for balsam mounts is 

 dammar dissolved in chloroform, because if it is in- 

 clined to run under the cover it will readily mix with 

 the mounting material without leaving a visible trace 

 behind. It is better to apply the brush to the edge of 

 the cover almost dry, the slide on the turn-table being 

 made to spin rapidly round, so as to create a track in 

 which the dammar solution will readily flow. The second 

 application is made immediately to follow the first, 

 with the brush full, so that there will be a small drop 

 of solution on the end, and this is allowed to touch the 

 edge of the cover without letting the brush itself come 

 in contact with the glass. This process must be 

 repeated until the ring is built up to the proper size. 

 In drying, however, the ring of dammar will shrink 

 considerably, and thus it is necessary to make a subse- 

 quent application in a few hours' time. 



Wash away all surplus glycerine by syringing, then 

 apply a ring of a waterproof cement around the cover. 

 Such a cement may be bought under the name of Bell's 

 cement. A better and less expensive cement may, 

 however, be made by dissolving 10 grs. of gum-ammo- 

 niac in 1 oz. of acetic acid (No. 8) ; then add to this 

 solution 2 drachms of Cox's gelatine. This liquid 

 flows easily from the brush and is waterproof, rendered 

 more so if subsequently brushed over with a solution 

 of 10 grs. of bichromate of potash in 1 oz. of water. 

 But what especially recommends this cement is its 

 adhesive power to glass, even should there be a little 

 glycerine left behind on the cover. After the gelatine 

 ring is dry any kind of cement may be employed. 

 When a considerable number of different objects are 

 being prepared at the same time, write the name of 

 each with pen and ink upon the glass slide. 1 

 .. Mounting Polyzoa. Mr. Morris, of Bath, has suc- 

 [ ceeded in obtaining beautiful specimens of polyzoa and 

 Mr. C. Seller, Microscopical Jourm.* 



