Page:Collier's New Encyclopedia v. 03.djvu/400

LEFT DIALYSIS 346 DIAMOND cient philosophers as a medium for ex- pressing their thoughts on subjects. The "Dialogues of Plato" are the finest ex- ample. DIALYSIS, a phenomenon observed by Thomas Graham in the middle of last century, consisting in the passage through an animal membrane or parch- ment of solutions of crystalloids, such as salt or sugar. He carried out his ex- periments by placing the dialyzer (i. e., a vessel having a bottom made of parch- ment) in a larger vessel filled with water. He then found that when a crys- talloidal solution was poured into the dialyzer, the substance in solution would pass through the diaphragrm into the water in the outer vessel. Colloidal solutions, however, would not pass through such diaphragms and so Gra- ham was able to separate colloidal from crystalloidal substances by this means. DIAMAGNETISM, the moving of bodies such as iron, when placed in a Geraes. It is the center of a rich dia- mond district; has manufactures of cot- ton and goldware, and is the seat of a Roman Catholic bishop. Pop. 13,000. DIAMETER, in geometry, a line drawn passing throu^ the center of a circle or other curvilinear figure, and terminating each way in the circumfer- ence. That point which bisects all lines drawn through a figure from side to side is called a center, and every line drawn through a center and terminating in the circumference or opposite boundaries is a diameter. Every circle has an infinite number of diameters. A diameter which is perpendicular to the chords which it bisects is called an axis. A circle has an infinite number of axis, every diameter being an axis. The parabola has one axis and each of the other conic sections two axes. DIAMOND, a natural form of carbon, highly valued as a precious stone when transparent and of the crystalline form. 1. Top of rose cutting 2. Side of rose cutting 3. Briolette cutting DIAMOND CUTTING 4. Brilliant cutting- field of magnetic force, from places of weaker to places of stronger force. The opposite is true of bismuth and other substances. Such substances are said to be diamagnetic. DIAMANTINA (de-a-man-te'na), a town in the Brazilian province of Minas top 5. Brilliant cutting — side 6. Brilliant cutting — back view A diamond crystallizes in the cubic or monometric system, its common form bein^ the regular octahedron or a modi- fication of it. The bases are often curved and the general form of the crys- tal is more or less rounded. The surface of the diamond frequently exhibits striae and triangular impressions, while the in-