Journal of applied microscopy and laboratory methods . surfaces, even when these were blackened with the 1114 Journal of Applied Microscopy greatest care. This trouble was overcome satisfactorily by dispensing with theflat surfaces; i. e., by making them on a bevel, with only the sharp edge toreflect the light. To do away with the difliculty arising from the small depth of focus, the onlyway found was to stop down the lens. As the depth of some objects is very great in proportion to the focal lengthof the lens, it necessitates the use of a very small stop. The smallest stop usedby me for this
Journal of applied microscopy and laboratory methods . surfaces, even when these were blackened with the 1114 Journal of Applied Microscopy greatest care. This trouble was overcome satisfactorily by dispensing with theflat surfaces; i. e., by making them on a bevel, with only the sharp edge toreflect the light. To do away with the difliculty arising from the small depth of focus, the onlyway found was to stop down the lens. As the depth of some objects is very great in proportion to the focal lengthof the lens, it necessitates the use of a very small stop. The smallest stop usedby me for this work has a diameter of y^f „ of an inch, and the edges of theopening are made nearly sharp and carefully blackened. The rear of the lenshas also to be guarded to prevent reflections which in this work would be veryserious. Of course, the time of exposure requires to be lengthened in proportionto the size of stop; many times the exposure has taken over thirty minutes,and as each exposure must be made separately on the plate, the time will Figure 2. Suppose the object to be photographed is a small living insect. It is placedunder a tumbler which has a small hole drilled through the bottom. Throughthis opening is injected a small quantity of ether. This soon places the insectin a condition to be handled. We then set it up on its feet in a position as nearlylife-like as possible on a small piece of opalin glass, and, to hold it in position,each of its feet is fastened down by means of wax. This is done by using a verysmall tool, heated in the flame of a spirit lamp. After the feet are fastenedproperly, the insect is placed in strong fumes of cyanide of potassium to end itslife. The surplus wax is now carefully removed by scraping it away with a finepointed knife. The object is now ready for the camera, and upon the pedestal in front of thelens the mounted object is made fast. The pedestal, upon which the mountedobject is fastened, has a rack and pinion movement, so as
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
