Bunten’s Barometer.—This instrument differs from the preceding but in one point, namely, that the capillary tube is formed of two soldered pieces, of which the one, passing into the other, is terminated by a capillary point. This arrangement is exhibited by [pl. 2], fig. 2.
Barometer pierced laterally for Demonstrations.—Take a tube thirty-nine inches long, with thick sides, and two-tenths of an inch internal diameter. Seal it at one end, and choke it at the distance of eight inches therefrom. Pierce a hole in the tube about twelve or sixteen inches from the choked part, and solder to the hole an additional piece, which can be closed by a cork or covered by a piece of bladder. The instrument is represented by [pl. 2], fig. 15.
Bell-Glasses for Experiments.—These are pieces of tube sealed at one end, and widened or bordered at the other. They are extremely useful, and much employed in chemical experiments. They also supply the place of bottles for preserving small quantities of substances. Sometimes they are required to be straight, as [pl. 3], fig. 12. Sometimes they need to be curved, as [pl. 3], fig. 29. This is particularly the case when they are to be employed as retorts, for which purpose the sealed part should be made thin. [Pl. 3], fig. 6, exhibits a retort with a tubulure.
Blowpipe.—We shall give in this article an account of the various pieces of glass which form part of the blowpipe described in the early part of this work. See [pl. 1], fig. 19.
The beak C, which is employed with the candlestick, is merely a bent tube, at the extremity of which a bulb is blown. The bulb is terminated by a point, the thickness of the sides of which is augmented by turning it for a long time in the flame.
As for the beak used with the lamp, it is simply a bent tube C´, of which the orifice has been diminished by turning it round in the flame. The point of this beak is not drawn out like that of the beak described in the preceding paragraph, but is allowed to be thick, that it may not melt in the flame of the lamp.