Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/464

432]  it there to the action of a vacuum, and of a pressure superior to that of the atmosphere. This was effected with a view to extract, by the vacuum, whatever elastic fluid may remain in it, under the ordinary pressure; and also to increase the solidity and whiteness of the substance, by the superior weight applied to it, when cooling.

From the very great utility of candles, they early became the object of adulteration: hence it is provided by various acts of parliament, that all adulterated candles shall be forfeited; and if any tallow-chandlers, or melters, make use of melting-houses without giving due notice to the excise-officers, they shall be subject to a penalty of 100l.; or, if they fail in informing those persons of their making candles, and thus prevent them from ascertaining the duties, 50l.; and if any person is convicted of making candles privately, they are forfeited, together with the utensils, and 100l. by. the 5 III. c. 43. Those candles, however, for which the duty has been paid, may be exported, and the duty allowed; but, by the statutes of 8, c. 9, and 23 II. c. 21, no drawback is allowed on the exportation of foreign candles.

Although candles are preferable to lamps, as their light is less injurious both to the eyes and lungs, and as they do not produce so great a volume of smoke, yet a clean chamber-lamp, which emits as little smoke and smell as possible, is far superior even to wax-candles; for, 1. As all candles burn downwards, the eye necessarily becomes more fatigued, and strained during the later hours of candle-light; 2. Because they yield an irregular light, which occasions the additional trouble of snuffing them; and lastly, because, if the air be agitated ever so little, or if the candles are made of bad materials, they injure the eye by their flaring light.  . See White.  . See.  CANKER, a disease to which trees are subject; it proceeds principally from the nature of the soil, and causes the bark to decay. If the canker be seated in a bough, and a large one, the general practice is to cut it off at some distance from the stem; if a small one, close to it.

When the tree is thus open and exposed, it is liable to receive injury from the air, moisture, and insects. To prevent this, white lead and boiled oil, made into a kind of thick paint, with the addition of sublimate of mercury, has been recommended by Dr., as an useful remedy, especially when applied to the wounds of those trees, the wood of which contains less acrimony, and is consequently more liable to be penetrated, and eaten by a large worm or maggot, that would otherwise consume the whole internal wood.

In the 13th vol. of the Transactions of the Society of Arts, &c. the ingenious Mr. observes, that, in pruning, this medication ought never to be omitted, as experience has demonstrated, that mercury removes the noxious effects of canker in the more delicate fruit trees, so effectually as to influence the vegetation of plants, by affording both smoothness and a free growth to the bark.

He directs every stump, together with the decayed or blighted branches, and all those that cross the