In reading the height of the columns, the eye is so placed that the division of the scale nearest to the water level bisects the reflection of the retina The determination of the specific gravity of solids in the mirror. The level of the water can then be and liquids is one involving many precautions, if ac-read off within a small fraction of a millimeter. The curate results are to be attained. Water is the fluid to be tested is poured into the left hand tube, basis, its temperature being placed at 4° C. In prac