751. As iron is the root of all metals, so every division or group of ore has a principal metal, which occurs in more considerable quantity than the rest and characterizes the division. Among the saline ores, copper under the form of malachite is the principal metal. Its fusing point is 6000F. Among the sulphurous ores, _lead_ is the chief metal; it has with its neighbours the lowest grade of fusion, which may be set down in round numbers as 600F. Among the volatile, arsenic is the principal metal. 752. Among the standard metals, silver is the principal metal; it has with its affinities a fusing point, which ranges midway between that of iron and lead, being probably about 5000F. 753. There are four grades of fusion of the metals, which are removed from each other by very wide intervals, between which no metal is situated. Quicksilver is fluid at the temperature of the air and becomes volatile like arsenic. Moreover the artificial metals are associated with the alkalies and acids. Lead, with its congeners, melts at 500F.; silver with gold and copper at 5000; iron, platinum and such like at 20,000. 754. There are four metallic characters, which are shown to be peculiar in all their relations, in their affinities for oxygen, acid, and sulphur, in respect to specific gravity, fusibility, extensibility, in their electric relation, in mode of fracture, in occurrence, age, and geographical distribution, &c. c. POISON. 755. It is a remarkable fact that the principal metal of the elemental metals, obtains mostly by oxydation or acidification poisonous properties, while the proper earth-metal, iron, acts beneficially upon the animal organization. Among the water-metals lead becomes poisonous by acidification; among the fire-metals mercury. Among the air-metals arsenic ranks highest, becoming poisonous by mere oxydation. Among the earth-metals, only one among the salt-metals is poisonous, and that is copper. 756. The metals thus appear to become poisonous, when they enter into or put on the character of salt, or of water. 757. The above are also those very metals, which unite most readily with the others, to form alloys, amalgams or metallic compounds. Copper is very readily alloyed; lead almost always contains silver; mercury is susceptible of amalgamation; arsenic metallizes the others almost like sulphur. 758. The air-metals appear to have lost for the most part the metallic character; arsenic therefore destroys also magnetism. 759. The essence of metallic poison thus appears to reside in the endeavour on the part of the metals to suppress the metallic character and convert themselves into the formless elements. The metallic poison is the direct opponent of the metals themselves, and through this, of everything that has form, and thus of the Organic also. d. MAGNETISM.