RAD′ICLE. Syn. Radical. According to the binary theory of the constitution of saline compounds, every salt is composed, like chloride of sodium (NaCl), of two sides or parts, which are termed its radicals. That part of a salt which consists of a metal, or of a body exercising the chemical functions of one, is called the metallic, basic, or basylous radical; while the other part, which, like chlorine, by combining with hydrogen would produce an acid, is designated the chlorous or acidulous radical. Every salt, therefore, consists of a basic and of an acid radical. Sometimes radicals are elementary in their nature, when they are called simple; and sometimes they are made up of a group of elements, when they are termed compound. Some radicals, both simple and compound, have been isolated, while many have but a hypothetical existence. In the following formulæ the vertical line separates the basic from the acid radicals, the
former being on the left, the latter on the right:—
| H | F | Hydrofluoric acid (Fluoride of hydrogen). |
| Na | Cl | Chloride of sodium. |
| K | CN | Cyanide of potassium. |
| Ca | CO3 | Carbonate of calcium. |
| NH4 | Cl | Chloride of ammonium. |
| C2H5 | NO2 | Nitrite of ethyl. |
RAD′ISH. The common garden radish (Raphanus, L.) is the root of Raphanus sativus (Linn.), one of the Cruciferæ. There are several varieties. They are all slightly diuretic and laxative, and possess considerable power in exciting the appetite. The seed is pressed for oil. The horseradish (ARMORACIA, L.) belongs to a distinct genus.
RAIN-GAUGE. Syn. Ombometer, Pluviameter, Udometer. An instrument for determining the quantity of water, which falls as rain, at any given place. A simple and convenient rain-gauge for agricultural purposes is formed of a wide mouthed funnel, or open receiver, connected with a glass tube furnished with a stop-cock. The diameter of the tube may be exactly 1-100th that of the receiver, and if the tube be graduated into inches and tenths, the quantity of rain that falls may be easily read off to the 1-1000th of an inch. The instrument should be set in some perfectly open situation; and, for agricultural purposes, with its edge as nearly level with the ground as possible. Another form of gauge is furnished with a float, the height of which marks the amount of liquid. The diameter of the gauge should range between 4 and 8 inches. The quantity of water should be duly measured and registered at 9 a.m. daily.
Mr Symonds, F.R.B.S., has drawn the following code of instructions for the guidance of those registering the amount of rainfall at any locality:—
1. Site. A rain-gauge should not be set on a slope or terrace, but on a level piece of ground, at a distance from shrubs, trees, walls, and buildings—at the very least as many feet from their base as they are in height.
Tall growing flowers, vegetables, and bushes must be kept away from the gauges. If a thoroughly clear site cannot be obtained, shelter is most endurable from north-west, north, and east; less so from south, south-east, and west; and not at all from south-west or north-east.
2. Old Gauges. Old-established gauges should not be moved, nor their registration discontinued, until at least two years after a new one has been in operation, otherwise the continuity of the register will be irreparably destroyed. Both the old and the new ones must be registered at the same time, and the results recorded for comparison.
3. Level. The funnel of a rain-gauge must be set quite level, and so firmly fixed that it