Notes on Micro-j^hotography. By Edward J. Gayer. 259 



scope may be altered at pleasure. The mode of procedure is as 

 follows. Uncover the round hole B, the source of hght (if sun- 

 light is used, this hole, together with the rest of the apparatus 

 attached to it, should have a vertical movement to allow for the 

 changing position of the sun), and place in front of it either an 

 ammonio-sulphate of copper or alum cell, or a piece of blue glass, 

 according to the work you are going to do. Adjust the mirror D, which 

 is best made of silvered glass with the polished silvered side up, and 

 connected with a ball-and-socket joint to a firm but movable stand 

 on the table. Place the large condenser in the path of the rays as 

 close to the mirror as may be convenient, and at such a distance 

 from the microscope that the rays of light shall cross before enter- 

 ing the achromatic condenser of the microscope. This large con- 

 denser E should be an achromatic lens, of moderate focus, and as 

 large as possible, not less than 3 inches in diameter, and not more 

 than 10 or 12 inches focus. A photographic landscape lens 

 answers well. Adjust the achromatic condenser of your microscope, 

 the object, stage, and objective. Place your dark slide open in the 

 holder at the other end of the table with an unprepared plate 

 in it, on which you have previously evenly pasted a piece of white 

 albumenized paper, and on which you have drawn two diagonal 

 lines from corner to corner of the plate, in order to show its centre, 

 and on which at the centre you have either neatly written or 

 pasted a word in small type. Adjust your telescope N so as to 

 view this word in perfect focus, and then leave it so. This tele- 

 scope is best made out of the object-glass of a large opera- glass 

 and the eye-pieces of your microscope, by connecting the two with 

 tubes of sufficient length to allow of considerable throwing back of 

 the conjugate focus of the object-glass, a necessary result of your 

 viewing the plate at a distance of a few feet and your telescope 

 object-glass receiving divergent instead of parallel rays. Then still 

 looking through the telescope, which is a fixture, being made to 

 slide stifily through a hole in the fixed front of the camera K, 

 focus with the fine and coarse adjustments of your microscope, and 

 bring the object into its proper place on the screen of albumenized 

 paper, the centre of which is abundantly apparent owing to the 

 word and the cross lines, and is a very easy substance to focus on. 

 Having made all adjustments, remove your dark slide with the 

 focussing screen in it, shut the hole B by a shutter from outside 

 the window worked by cords. Prepare your sensitive photographic 

 plate, with which you replace the plate covered with albumenized 

 paper, and put the closed dark slide into the place where you took it 

 from, and put a piece of white cardboard M into the groove close in 

 front of the dark slide ; open the shutter and arrange the light finally 

 on the cardboard. Place a book or other shield in front of the 

 large condenser E in the path of the rays, so as to shut off the 



