and Laboratory Methods. 1285 



device of attaching a disk of cover glass to the ground slide with Canada balsam 

 will offer a perfect surface for delicate focusing. A sheet of plain glass may be 

 substituted for the focusing screen, or the atrial image may be found by means 

 of a hand lens. The illumination may be obtained by means of a coal oil lamp 

 standing at such a height as to bring the center of its flame up to the optical 

 axis of the microscope. 



For many years I have been profoundly impressed with the importance of 

 photo-micrography as an educational agent which the successful introduction of 

 the half-tone process of reproduction greatly intensified. At first the great 

 cost of everything necessary for the work was no doubt a bar to its more general 

 introduction, but happily this no longer exists. Quite recently one of a type of 

 student's microscopes generally adopted by our best institutions of learning fell 

 into my hands. It was a revelation to me of the wonderful progress made in 

 the mechanism and optics of the microscope, and made my own apparatus, only 

 some two decades old, seem quite ancient in comparison. Yet some of the 

 objectives of my outfit represented an outlay of much more than the cost of this 

 entire apparatus. 



The microscope in question was fitted with two eyepieces, 2/.3 and 1/6-inch 

 objectives. Abbe condenser and iris diaphragm ; a plain working stand, as will be 

 seen, costing very little money but of admirable workmanship throughout. 



My test of a microscope and objectives being their adaptability to photography, 

 I proceeded to apply it to this outfit, but came a shade further than usual in 

 discarding the use of my special camera, and making up, instead, an impro- 

 vised affair, that anyone can do for himself in a very few moments. A small 

 quarter-plate camera was pressed into the service, secured to a block at just the 

 proper height to bring its axis in line with that of the microscope. An old 

 focusing cloth wound around the tube of the microscope at its junction with the 

 camera, made this light tight. A coal oil lamp with an inch flame adjustable to 

 any height afforded the necessary illumination for most of the tests, though the 

 far more actinic light of an acetylene flame was also used at times. 



With this very simple apparatus, I made a number of negatives, mostly of 

 tissues normal and diseased and varying in amplification from 100 to 500 

 diameters, the range of most useful enlargements in that class of work. While 

 these might perhaps be exceeded in absolute perfection by the employment of 

 the very highest attainable excellence in optical appliances, my conclusion is that 

 they are good enough for all practical purposes, and quite within the means and 

 ability of every student to make for himself in illustrating his own microscopical 

 work. For this reason it is urged upon everyone to make the attempt. 



Among these negatives are two which may serve to illustrate the excellence of 

 the optical work of this microscope. Both were made by the aid of the usual 

 Huyghenian eyepieces furnished with the instrument, a form that we are told in 

 the books is totally unsuited to the purpose. One was made with the Abbe 

 condenser, a form which we are likewise told is useless in photography. But 

 negatives and prints tell a different story. It is obviously impossible to give a 

 detailed account of their working, within the limits of space at my disposal ; but 

 a synopsis may prove useful to many seeking information on the subject. 



