26 THE MICROSCOPE. [February, 



is thick it will stay rolled and you have an excellent shade which, 

 by being white, reflects the light much better than a mirror. 

 To make the modifier. I use a slide 3 inches by 1 inch, of 

 ground glass, and this can be gotten very cheaply. If it is not 

 ground fine enough it can be rendered more finely ground, and, 

 in fact. I think it well to do so, by wetting always with glycerin, 

 or it can be varnished with copal or other white varnish. I also 

 coat another slide of ground glass with a varnish, copal or other 

 white varnish, colored blue. It is colored with blue dye such as is 

 sold for ten cents at the apothecaries. This is all. The lamp 

 and the modifier do not cost 25 cents. That is cheap enough 

 and I know it is efficient. 



I now will describe a contrivance for centring and mounting 

 microscopic objects. A brass slide is made of '-'- brass rule " such 

 as printers use for type. It is an inch wide, for that is the height 

 of tvpe and the width of the slide also. Cut it three inches long. 

 The thickness does not matter much, but if as thick as a glass 

 slide it will do. This has ruled on it with a steel point (the 

 point of a file will do) two lines from corner to corner, cutting 

 each other at the centre. This is the place where the cover is 

 placed and this is. of course, immediately in the centre of the 

 slide. An '• American clothes-peg " is used to hold it over the 

 source of heat. A slide is placed on the brass slip and is fixed 

 there by the clothes-peg. It is then heated, and the brass, being 

 a good conductor of heat, conveys all the heat over the whole 

 slide, and we run no risk of breaking it. When it is heated 

 enough with the object on the slide a drop of gum thus, which 

 is the medium I use entirely, is placed on it. The alcohol is 

 boiled off* and the cover put in place. With this mounting ap- 

 paratus we do away with the risk of overheating and so of break- 

 ing: the slide, and as it retains the heat for some time the mounted 

 object can be arranged very nicely. I use this little contriv- 

 ance very commonly, and I hope that it will meet the wants of 

 microscopists who mount objects themselves. 



The cost of slides and covers is high. They can be made of a 

 substance much cheaper, and possess properties which glass has 

 not. In using celluloid, which is wood rendered soluble in ether 

 and alcohol with gum camphor, for films for microphotography 

 I was struck with some of its properties. It is transparent, un- 

 breakable, light weight, and occupies very little room. It is strong 

 as wood, has no fibre, and can be cut readily with scissors. It 

 can be obtained with a ground surface as well as plain, and the 

 cost is a trifle. Very thin celluloid films are used for instantaneous 

 photographs, and this can be employed for both, whilst the thicker 

 kind used for ordinary photography makes capital slides. I have 

 some an inch square which I use in this way, mounting it tem- 

 porarily in a glass slide for use on the microscope. 



