The bulb being heated, its tube is to be immersed in the alcohol : the partial vacuum, produced within it by cold, will cause the atmospheric p lG 143 pressure to force in some alcohol.

It is then to be placed in a fluid, which boils at a higher tem- perature than that, to which the vapour must be raised: chloride of zinc, the boiling point of which is very high, answers, for the purpose, in some cases ; but, in others, it will be necessary B to use fusible metal, which is made by melting together eight parts, by weight, of bismuth, three of tin, and five of lead.

The bulb, and the fluid, in which it is immersed, should now be raised to the required temperature ascertained by a thermo- meter ; and, when nothing but vapour remains in the bulb, its capillary neck is to be hermetically sealed, with the flame of a lamp urged by the blow-pipe.

It is, then, to be cooled, and weighed : the vapour will be condensed ; but this is of no consequence, since there will be nothing else in the interior of the bulb.

The contents of the latter, in cubic inches, may be found, by breaking off the fine point of the tube under the surface of mercury, and allowing the whole interior to be filled with that fluid which is, then, to be poured out, and measured.