MOUNTING IN BALSAM. 297 



We will here go through the operation of mounting a 

 rock section in undiluted balsam, just to illustrate the only 

 case in which the author advises the use of papers to cover 

 up the whole of the slide. 



A hot-water plate is used by a great many mounters. 

 It may be a tin box 9 inches square by 2 inches in depth, 

 supported on a stand or upon four legs. In one corner is a 

 funnel-shaped neck for the introduction of water and the 

 escape of steam when in use, the chest being heated by 

 means of a gas-burner or spirit-lamp. 



Bell-jars are sure to be required for many purposes, but 

 principally for keeping the dust from objects which are 

 undergoing preparation. They neeo? not be large, and 

 broken wine glasses may be well utilised for this purpose 

 if the stem only is broken. 



When speaking of the hot- water box, perhaps we should 

 have mentioned the hot plate, which is still a favourite 

 with many mounters, who still cling to undiluted balsam. 

 This is a brass plate, standing upon four legs, and is 

 usually heated by means of a spirit-lamp, though there is 

 no reason why it should not be heated by gas. 



The reader will remember that when treating of section- 

 cutting, the surface of the slice first polished was to be 

 cemented firmly to a glass slip, the final grinding being 

 performed upon it. When grinding a section to extreme 

 thinness, the slip is often badly scratched, and thus dis- 

 figured ; some operators advise the section to be taken off 

 this slip, and put upon another for permanent mounting, 

 but in many cases this is not admissible, and the following 

 method should be adopted. Take the glass slip with the 

 section upon it and clean the surface with water, and 

 after with methylated spirit ; place a tiny drop of balsam 

 (rendered fluid by heat) upon the centre of the section, 

 carefully put on the cover and place the whole on the 



