HYDROSTATICS.

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body in air, and W' its weight in water, thenW-J-tm (W — W') is its weight in vacuo verynearly.

In the mean state of the atmosphere, m =.00122nearly.

252. If ^ be the specific gravity of a body, as-certained by weighing it in air and water, andm be the specific gravity of the air at the timewhen the experiment was made ; the correct spe-cific gravity, or that which would have beenfound if the body had been weighed in a vacuuminstead of air, is s in (1 — s).

When the body is heavier than water, this correctionis subtractive ; when lighter, it is additive.

The manner of finding the specific gravity of air willbe afterwards explained.

253. If B be the bulk of any body in cubicinches English , W its weight in grains, andS its specific gravity, that of water being 1 ;

_ VV

B “(25l7576)S*

This theorem is founded on an experiment of Sir G.Shuckborough’s, (Phil. Trans. 1798), by whichthe weight of a cubic inch of distilled w r ater, of thetemperature 66°, was found to be 252.422 grains,which, reduced to the temperature 60°, is 252.576.Cavallo, vol. ii. p. 98.

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