88 PRACTICAL MICROSCOPY. 



the introduction of colouring matters, as carmine and 

 indigo ; and lastly, its moderate cost and durability. 



For Confervae, small Infusoria, and similar organisms it 

 is sufficient to place the object on the bottom glass, with a 

 drop of water, and apply the covering glass in same manner 

 as when using a glass stage-plate. When a thicker layer of 

 water is required, a narrow ring of vulcanite, cork, or other 

 suitable material, of the requisite thickness, should be placed 

 on the lower glass, and the object put in position, the cover- 

 ing glass being finally applied as in mounting objects in a 

 cell. The supply of water can be maintained by putting a 

 drop occasionally in one of the side " wells," keeping the 

 slide, when not under examination, in a small damp cham- 

 ber, to prevent evaporation. To change the water, supply 

 through one "well," and draw out through the other by 

 means of a roll of blotting paper. 



Messrs. Thompson and Capper, of Liverpool, were the 

 original makers of this slide, and also of BotterilFs zoophyte 

 trough, illustrated at Fig. 75. 



The ordinary slip with a ledge of glass cemented to its 

 lower edge, as shown in Fig. 77, is very useful, and saves the 



stage of the microscope 



from corrosion when marine 



. , . 



organisms are being ex- 

 amined ; it may easily be 

 constructed by the student. 



The glass for the construction of these troughs and slides 

 may easily be cut with a glazier's diamond, and the edges 

 ground parallel upon the flat face of an ordinary grindstone 

 kept well wetted with water, or even by rubbing them 

 upon a flat well-moistened piece of Yorkshire flagstone. 

 An emery wheel will also answer the purpose. Pieces of 

 superfluous glass may be removed by the use of a fine cut 

 file lubricated with oil of turpentine, and holes made with 



