BLOW, in a general sense, denotes a stroke given either with the hand, a weapon, or instrument. In fencing, blows differ from thrusts, as the former are given by striking, the latter by pushing.
Military Blow, alapa militaris, that given with a sword on the neck or shoulder of a candidate for knighthood, in the ceremony of dubbing him. The custom seems to have taken its rise from the ancient ceremony of manumission. In giving the blow, the prince used the formula Esto bonus miles, "Be a valiant soldier;" upon which the party rose a complete knight, and qualified to bear arms in his own right.
Blow, in law. See BATTERY.
Fly-Blows, the ova of flies deposited on flesh, or other substances proper for hatching them.
Blow-Pipe, among jewellers and other artificers, is a glass tube, of a length and thickness at discretion, wherewith they quicken the flame of their lamp, by blowing through it with their mouth. It is used in works of quicker dispatch, which do not need the bellows. Though the wind blown out at a small bent tube of glass, called a blow-pipe, seems not to have any great celerity, in comparison of the parts of flame, and is itself of little force; yet, when the flame of a lamp or candle is directed by it, so as to beat upon a body at a convenient distance, it may be made to melt silver, or even copper itself, which yet may be kept, for many hours, unmelted in a red-hot crucible, or the flame of the lamp or candle unassisted by the blast. The enamellers have also tubes of divers sizes, wherewith to blow their enamel, answering to the same purpose as the pontillo, or blow-pipe, of glassmen.
The blow-pipe has also been a little used by chemists and mineralists. But Mr Cronstedt has lately extended its use to the examination of all mineral bodies; which by means thereof, with a candle and piece of charcoal, may, in portions sufficient for mineralogical experiments, be burnt, calcined, melted, or scorified, &c. as well as in any great works.—This instrument is composed of two parts; and this for the facility both of making, carrying it along, and cleansing it in the
inside when necessary. The two parts are represented separate †, and of the true size; the figure of the instrument, when these are put together, may be easily conceived. The globe a ( 2.) is hollow, and made on purpose to condense the vapours, which always happen to be in the blow-pipe when it has been used some time: if this globe was not there, the vapours would go directly with the wind out into the flame, and thereby cool the assay. The hole in the small end b, thro' which the wind comes out, ought not to be larger than the size of the finest wire. This hole may now and then happen to be stopped up by something coming into it, so as to hinder the force of the wind: one ought therefore to have a piece of the finest wire, to clear it with when required; and, in order to have this wire the better at hand, it may be fastened round the blow-pipe, in such a manner as is represented in 1: c is the wire fastened round the blow-pipe, and afterwards drawn through a small hole at e, made in the ring f, to keep it more steady. In order to determine the most convenient proportions of this instrument, several blow-pipes of different sizes, both bigger and smaller, have been tried: the former have required too much wind; and the latter, being too soon filled with the wind, have returned it back again upon the lungs: both these circumstances hindered greatly the experiments, and are perhaps even prejudicial to the health. The size here given is found to answer best; and though the hole must be as small as abovementioned, yet the sides of the pipe at the point must not be thinner, nor the point narrower, than here represented, else it will be too weak, and not give so good a flame. It is also to be observed, that the canal throughout the pipe, but particularly the hole at the small end, must be made very smooth, so that there be no inequalities in it; the wind would else be divided, and consequently the flame made double. That blow-pipe is to be reckoned the best, through which can be formed the longest and most pointed flame from off a common-sized candle. These blow-pipes are commonly made of brass or silver. The manner of using them in mineralogical experiments are explained under the article MINERALOGY.