METHOD OP MOUNTING OBJECTS IN FLVn:). 



299 



Fig. 202. 



FiK. 203. 



fig. 202 ; around the hole a channel or 

 groove is made, the object of which, as 

 in Mr. Barker's, shown by fig. 117, is 

 the prevention of the entrance of the 

 cementing material within it. Another 

 form calculated to answer a similar pur- 

 pose, is shown by fig. 203 ; in this the 

 hole does not extend through the glass, 

 and the bottom of it may be either 

 polished or rough ; on the under surface 

 of the cell there is a groove as in fig. 

 202, so that when marine-glue is em- 

 ployed to fasten it to a slide, the glue 

 will be all kept outside the groove, and 

 an object contained in a cell of this 

 kind can, if required, be examined by 

 transmitted light. 

 Whilst treating of the difierent forms of cells and boxes for 

 containing large preparations that require the aid of the 

 microscope for their due exhibition, it may be as well here to 

 allude to the method employed by Mr. Dennis, the manufac- 

 turer of these boxes for Mr. Goadby and others, to render 

 them better fitted to withstand the expansive power of the 

 fluid they contain ; for this purpose he has found it necessary 

 to strengthen the joinings of the sides and ends by what he 

 terms angle-pieces ; these are slips of plate-glass, ground into 

 a three-sided prismatic shape, which are cemented to the inside 

 of the box, so as to fiU up all the angles made by the sides 

 and bottom, and the ends and sides, and likewise to strengthen 

 the joints on the outside, by cementing strips of plate-glass 

 over them, in order to prevent the sides from bursting 

 outwards. Although this is a tedious process, the operator, 

 nevertheless, will be well repaid for his trouble by the greater 

 durability of the work. 



The method of cleaning the inside of the box, and the 

 putting on of the cover, is the same as has been described in 

 the smaller cells; to get rid of air bubbles, it is advisable to 

 pour into it much more fluid than is required to fill it. 



