. Bulletin of the Geological Society of America. Geology. 510 A. C. LANE MINE WATERS AND THEIR FIELD ASSAY totally reflected up to an angle dependent on the relative indices of A and B. Tims an objective, D, has part of the field more illuminated than the rest. These parts are separated in daylight by a horizontal colored band. The mine lights are generally more nearly monochromatic. It is perhaps well, by cementing a bit of yellow glass or celluloid, to have the light at C nearly monochromatic. The image of the field is found at E, and there a scale is placed which is viewed by the ocular F.
. Bulletin of the Geological Society of America. Geology. 510 A. C. LANE MINE WATERS AND THEIR FIELD ASSAY totally reflected up to an angle dependent on the relative indices of A and B. Tims an objective, D, has part of the field more illuminated than the rest. These parts are separated in daylight by a horizontal colored band. The mine lights are generally more nearly monochromatic. It is perhaps well, by cementing a bit of yellow glass or celluloid, to have the light at C nearly monochromatic. The image of the field is found at E, and there a scale is placed which is viewed by the ocular F. Light should be cut off from entering except by C, by shading by the hand or otherwise. Down in the mine, the sole illumination being from a lamp or candle held a little below C, this causes no Figure 1.—Outline of Pocket Total Seflectomefer Outlines of Instrument In full line. The course of a ray from C through the glasa prism, reflected at the angle of total reflection, reading the scale E, Is In dots. The part of the scale above will be more illuminated. TABLET METHODS U. S. Geological Survey method.—In following the example of the physicians and having reagents put up with known quantities in tablet form, the U. S. Geological Survey-^ has performed a real service, which enables one to carry in a pocket the chemicals to make three or four im- portant tests. It seems to me this method is capable of much greater development. It must also be remembered that by dissolving a tablet in a known quantity of water a solution of known strength may be obtained, and this is often the most convenient method, if a numl3er of tests are to be made at a time. The accuracy of most of these methods is dependent upon the accuracy with which a quantity of water varying from 20 to 100 cubic centimeters can be measured, and is something like 1 to 5 per cent. Chlorine.—Leighton's method seems all that could be desired in deli- cacy, accurac}', simplicity, and convenience. It is f
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890
