'Transactions of the Bombay Geographical Society, from September 1850 to June 1852. Edited by the Secretary. Volume X.' [‎6] (25/458)

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PROCEEDINGS OP THE SOCIETY,
stirrup carries a stout brass wire, to which the counterpoise is hooked. This exactly
balances the beam when the cylinder and vase (with Thermometer attached) are filled with
distilled water. There is a contrivance fixed to the upper and back part of the standard
actuated by a screw, by which the knife edges can be raised from the planes ; and the beam
has two notches on its lower surface, which are received upon two teeth on the arms of the
lever, so that, when liberated, the beam can always be brought to the same part of the
planes. The whole stands on a mahogany board with three levelling screws, a spirit level
at the back, and weights from £ to 550 grains in a row in front. The beam, though light
sustains 12,000 grains, and will then indicate the addition of a J of a grain—or the
48,000th part of the load. It is as exact as can well be, the difference between the two
arms not amounting to one 20 th of a grain. I regret that I had not another thermometer
to spare for attachment to the standard, as the temperature of the air must be registered
conjointly with that of evaporating surface.
The directions for using this instrument are very simple. The vase is filled up to the
upper part of the opening in it, and the cylinder is unscrewed from the vase, and by re
versing it the valve falls back, the water is then poured in, and the valve, upon inversion
comes again into play and prevents the escape of the water. It is then screwed into the vase!
Should the whole now weigh more than counterbalances the given equipoise, a small quan
tity of the water can be removed by the corner of a handkerchief, and the true balance ad
justed ; or, if found wanting, a few drops can be added. To make certain that no air ex
ists at the mouth of the valve, and intercepts the connection between the water in the cylin!
der and that in the vase, it is as well to tilt up the cylinder margin of the vase, and pass U p
the bubble of air, if one be present, or the same end may be effected by a straw or wire
passed through the opening in the vase into the hollow male screw. This will liberate the
bubble equally well, although with careful manipulation no air should lodge at the point
of junction-,