Journal of Applied Microscopy. 557 



chair, and accordingly the left arm was cut away and suspended on a hinge so 

 that it might afford a free entrance to the chair and yet be in a condition to be 

 swung back, to serve as a rest for the left arm of the operator. All the 

 wood-work was then painted black in order to do away with disturbing reflections. 



When it is desired to use the apparatus, the observer places the microscope 

 on the shelf provided for that purpose, and inclines it until the stage becomes 

 level with and parallel to the drawing surface. He then swings out the left arm 

 of the chair, seats himself, and returns the swinging arm to its closed position. 

 Thus situated, he finds both arms supported at about the level of the elbows 

 and the ocular of the microscope at a suitable height for comfortable observation. 

 When the camera lucida is employed, the image is traced upon paper fastened 

 to the pine drawing board by long, stout pins thrust into the soft wood. The 

 right arm, meanwhile, rests in a comfortable, natural position, and the hand 

 supports and guides the pencil as in writing. The accompanying cut makes the 

 various details of construction and operation plain. 



IHumination. — Ordinary sunlight is, in many ways, unsatisfactory. For 

 accurate compara'tive work, a more reliable and manageable source of light 

 becomes almost necessary. The writer has found the Welsbach incandescent 

 gas lamp eminently suited to the requirements of the microscopist. A very 

 excellent method of using it is to cast an image of the glowing mantle upon the 

 mirror by means of a balloon fiask filled with ammonio-cupric sulphate solution. 

 The flask acts as a condensing lens, and by mutually arranging it and the lamp, 

 the proper sized mantle image may be thrown upon the mirror. A turned 

 wooden base, bearing a hole in the center for the reception of the flask neck, has 

 proven the most satisfactory mounting, although improvised ones in the form of 

 tumblers or empty fruit jars have often served the purpose. 



The final character of the light is entirely dependent upon the solution in the 

 flask. This must be of such a nature that it will give a nearly white light 

 without the yellow of the gas-light or the blue of an excess of the ammonio- 

 cupric salt appearing. With the most careful adjustment, however, the light has 

 a cold bluish cast that obscures some details in sections stained by the iron- 

 haematoxylin method. The writer found by experiment that this difficulty could 

 be overcome and a beautiful soft white light secured by adding one or two drops 

 of a saturated alcoholic solution of safranin to the liter flask of properly diluted 

 ammonio-cupric sulphate solution. It has been found necessary to renew the 

 safranin every week or two, since it fa?Pes upon exposure. The light thus 

 modified leaves nothing to be desired, and has served in the most delicate work 

 with high powers. 



In connection with the chair previously described, a shelf is used for holding 

 the gas lamp and the flask condenser. This projects from the wall, somewhat 

 below the level of the microscope base, and with the bottom of the incandescent 

 mantle at a height of seven inches from the table, needs to be from twenty to 

 twenty-four inches long to permit the proper adjustments. 



Protection for the Eyes. — Almost as important as the illumination of the object 

 is the prevention of extraneous light from entering the eyes of the observer. 

 Nothing is more trying to the visual organs or more inimical to accurate obser- 



