198 The Microscope. 



ing the gauze with chloroform, covering it so that the fumes must 

 enter the bottle. For the subsequent operations the following outfit 

 will be required: 



Fluids. — Alcohol, Canada balsam, chloroform, liquor potassse, 

 oil of cloves and distilled water. Absolute alcohol is the best, but is 

 not so readily obtained, and in using will not long remain absolute. 

 The ordinary 94 per cent, will serve. Canada balsam, prepared with 

 chloroform, is the most suitable, as it does not require heat in use 

 and hardens sooner. . To prepare this, put the pure balsam in a 

 low, broad bottle and cover the top with paper to exclude dust, 

 then put the bottle in some warm place, avoiding much heat, which 

 will discolor the balsam. When quite hard dissolve with chloro- 

 form, making it thin enough to filter. After filtering it will soon 

 come, by evaporation, to a proper consistency, to maintain which 

 win require that chloroform be occasionally added. A good 

 method of keeping balsam is in one of the bottles described for the 

 purpose in W. H. Walmsley & Co.'s catalogue. 



In using balsam the writer has found no better way than with 

 an ordinary medicine dropper, with bent point. Press the rubber 

 top, and place the point in the balsam, which will fill the tube, when 

 pressure is removed; the balsam may then be veiy delicately applied 

 by slight pressure. After u.sing. press out the balsam and put the 

 dropper in place of the cork in an ordinary narrow-mouth ounce 

 bottle containing turpentine. By this means the dropper remains 

 clean. Press out the turpentine carefully before again using. 



The liquor potasste should be of officinal strength, viz. : 1 oz. 

 (Troy) fused caustic potassa and 1 pint distilled water. The oil of 

 cloves should be the best. When old it becomes too dark, and when 

 colorless it is generally impure. The proper color is that of pale 

 sherry. Distilled water is of course the best, but ordinary' clear water 

 will answer. All the fluids named should be filtered. If ordinary 

 filter-paper is used, run the fluid through two or three times, or some 

 of the fiber of the paper will be found in the result. Glass wool 

 is a very good filtering material and is cheap. Crowd a wad of this 

 into the tube of a small glass funnel and allow thq fluid to filter 

 through it. 



Three glass jars, about four inches high, and holding about 

 one-half pint each, are most suitable for holding the alcohol, turpen- 

 tine, and water when in use in the process to be referred to. These 

 should have close fitting stoppers to exclude dust, and in the case of 

 alcohol, to avoid as much as 2)ossib]e the lowering of its ju'oof. The 



