Apparatus for Determining the Specific Gravity of Minute Fragments of Minerals

Abstract

THIS is a contrivance designed to facilitate the measurement of the specific gravities of minute fragments of minerals by means of a diffusion column of methylene iodide, as described by Prof. Sollas in NATURE, vol. xliii. p. 404, and vol. xlix. p. 211. There is no new principle involved in the construction of the instrument. It is merely the adaptation to this particular purpose of a well-known device for getting rid of the error due to parallax, such as is employed in Prof. Joly's spring balance for determining specific gravities, and the best form of tangent galvanometer. The index, which in this case is a fine wire, or fibre of any kind, is reflected in a mirror placed behind it, the coincidence of the fibre and its reflection showing that the eye of the observer is exactly on a level with the index.