326 



H. MORLAND ON MOUNTING DIATOMACEJ2. 



will be useful for centering the slip with cover, and can after- 

 wards be rubbed off again ; note any curvature of slip, always 

 having the concave side for the under side. The next thing 

 required is to have the iron block, already described, duly 

 heated, and on this I place my two small pieces of brass about 

 one inch apart ; on the smaller I place the prepared cover, 

 which I slide off the ruled disk on " mounting slip " by means of 

 a piece of wood, as metal would injure the fine rulings. A drop 

 of styrax is now placed on the centre of the slip (on which the 

 small circle has been traced on the under side) and the slip put 

 on the hot block to drive away all trace of benzole. Whilst the 



Fig. 8. — A. Old book for preventing injury to table from hot block. 

 B. Iron block, 3" square and 2" thick. C. Piece of brass, 1" x %" x -|" thick. 

 D. Piece of brass, T y diameter x T y thick, with prepared cover-glass on 

 top. E. An ordinary 3" x 1" glass slip turned over, with drop of balsam or 

 styrax underneath. 



By pressing the slip E with the fingers of the left hand down on to the 

 piece of brass, C, whilst resisting slightly upwards with the right hand, the 

 slip can be lowered very steadily and accurately over the prepared cover on 

 piece of brass, D, without danger of crushing the arranged diatoms. 



Note. — If the iron block, B, has been heated for styrax mounting, it will 

 be necessary to have a small slip of wood, or other non-conductor of heat, 

 under the fingers of the left hand to prevent them from being burnt. 



slip is still hot it is turned over the prepared cover, as 

 in Fig. 10, duly centred with the cover and lowered care- 

 fully and gently until the styrax is just in contact, when, 

 if the heat is just right (only found out by practice, but some- 

 where about 180° Fahr.), the styrax will at once spread to the 

 edge of the cover, and the whole can be turned over again with 

 the cover uppermost ; if all be well the diatoms will not have 

 shifted, though when the slide comes to be examined under 

 the microscope a few bubbles may possibly be found. 

 To get rid of these all that is necessary is simply to let 



