518 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of those who seek to magnify every defect to be found in the work of 

 others whose results are not agreeable to the views or wishes of those 

 who so object. The identity of results by different methods, and 

 correlation of tests, may often show a given method to be practically 

 exact, yet, if any theoretical objection can be raised against it, it may 

 often be so treated as to completely discredit results that are in point 

 of fact accurate and reliable, and, unfortunately, the less scrupulous 

 the party who thus seeks to discredit such results, the greater the 

 success likely to attend his efforts." 



The foregoing, with other considerations, induced Mr. Vorce to 

 adopt the following method of micrometry for high powers : — Instead 

 of using extremely high-power objectives to gain great magnification, 

 tube length, as advocated by Dr. Beale, is employed, and the image 

 is viewed direct, i. e. without magnification by eye-piece, the method 

 having been suggested in part by former experience in the micrometry 

 of blood, and in part by experience in photo-micrography. A base- 

 board is provided, some four or five feet long, at one end of which 

 the lamp is placed enclosed in a light-tight box. A magic lantern 

 answers admirably for illumination, connecting its condenser tube 

 with the stage of the Microscope by means of a light-tight sleeve. 

 The Microscope is placed horizontally with the amplifier in place and 

 the tube as short as possible, and internally blackened to avoid 

 reflection. A movable vertical screen, faced with white cardboard or 

 glass, is adjusted on the base-board at such distance from the 

 Microscope as is found suitable, but need not ordinarily exceed two 

 feet, and is clamped in place when adjusted. The focusing stage is 

 adjusted on the Microscope stage, clamped in place, and a micrometer 

 is put in place and focused, the image being observed on the screen. 

 When the desired power is gained by moving the screen along the 

 base-board it is clamped in place, and the lines of the micrometer, as 

 seen on the screen, are traced by means of a ruler and pen on the face 

 of the screen, and by the use of dividers the spaces may be further 

 subdivided. In the measurements to be made the Microscope and 

 screen are not moved in the least, nor even touched, except to turn 

 the screws of the mechanical stage. The micrometer is removed by 

 pressing down the top plate of the focusing stage, the slide contain- 

 ing the objects to be measured is substituted, and the plate, on being 

 released, brings the slide into focus, if it is of the same thickness as 

 the micrometer, if not, it is brought into focus by the focusing 

 screws of the focusing stage. When focused, the image on the 

 screen is viewed and the measurement read off and noted as the slide 

 is passed along by the movement of the mechanical stage. If, owing 

 to uneven thickness or curvature of the slide or cover, the object 

 begins to pass out of focus, it is focused by means of the screws of 

 the focusing stage. The operator sits, ordinarily, near the screen, 

 working the stage with the left hand and noting the measurements 

 with the right ; the milled nuts of the focusing stage are easily 

 reached, and the work proceeds rapidly ; although two operators, one 

 to note down the measurements as called off by the other, and occasion- 

 ally changing places, facilitate the work. 



