. Elementary chemical microscopy . Fig. 121. Bausch & Lomb Optical Co. Filar Micrometer. by a micrometer screw provided with a graduated drum. As in the type just described one complete revolution of the drum is equivalent to 1 division of the scale within the eyepiece. The object to be measured is moved until the image fall under the scale and one edge in contact with one of the rulings. The number of whole divisions included within the image is recorded and the fraction of a division is ascertained by moving the cross- hair and reading the drum. For ordinary objects the first type descri
. Elementary chemical microscopy . Fig. 121. Bausch & Lomb Optical Co. Filar Micrometer. by a micrometer screw provided with a graduated drum. As in the type just described one complete revolution of the drum is equivalent to 1 division of the scale within the eyepiece. The object to be measured is moved until the image fall under the scale and one edge in contact with one of the rulings. The number of whole divisions included within the image is recorded and the fraction of a division is ascertained by moving the cross- hair and reading the drum. For ordinary objects the first type described is more rapid but for very tiny objects such as pigments, etc., the second type is more convenient and in the hands of the author some- what more accurate. Method 4. — Projecting a scale of known value into the field of view by means of substage condensers. This ingenious and prac- tically universal method appears to have first been suggested by Goring about 1820, and was rediscovered by Pigott in 1870, and employed by Sorby in refractive index determination in
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectmicroscopy, bookyear1
