AMBLYGONITE, a mineral usually found as cleavable, compact masses; it is translucent and has a vitreous lustre, and the colour varies from white to pale shades of violet, grey, green or yellow. There are good cleavages in two directions. The min eral is thus not unlike felspar in general appearance, but it is readily distinguished from this by its specific gravity (3.o) and chemical characters, being an aluminium and lithium fluophos phate, Li (A1F)PO,, with part of the lithium replaced by sodium and part of the fluorine by hydroxyl. Amblygonite occurs with lepidolite, tourmaline and other lithia-bearing minerals in pegma tite-veins. It was first discovered in Saxony in 1817, and later at Montebras, dep. Creuse, France, and at Hebron in Maine. More recently it has been discovered in considerable quantity at Pala in San Diego county, California, and at Caceres in Spain. AMBLYOPIA is a somewhat indefinite term meaning dimness of vision, or loss in the acuity of sight. It is usually restricted to those cases of dim vision which are not due to, refractive errors such as can be corrected by glasses and to cases in which there are no visible changes in the exterior or interior of the eye. Loss of vision may be partial or total, temporary or permanent. Total blindness is usually called amaurosis. The symptom may come on suddenly, with immediate total loss of sight, or gradually, with a sense of a blue veil or mist before the eyes, or it may not be noticed until the patient suddenly finds he cannot read. Colour blindness, night blindness, and day blindness are varieties of amblyopia. The causes may be injury to the brain, disease of the nervous and retinal structures involved in vision, drugs, and the poisons of certain diseases, such as chronic nephritis, acute ne phritis, toxemias of pregnancy, diabetes and malaria. Other common causes are intoxicating liquor, tobacco, lead, quinine and wood alcohol. It has long been recognized as a manifestation of hysteria and many cases were encountered during the war in soldiers suffering from "shell shock."