4.6 drams, the same solid body weighing in air 5

Multiply by 4 specific gravity of the solid

Product 32 specific gravity required.

It is a remarkable fact that a cubic foot of soft water weighs exactly 1000 ounces avoirdupois: and hence the Specific Gravity of any body multiplied by 1000 will be the weight of a cubic foot of that body.

And as 1728 cubic inches constitute a cubic foot, it follows that the 1728th part of the weight of a cubic foot of any body, must be the weight of a cubic inch of the same body. Wherefore 1000 ounces divided by 1728, will be the weight of a cubic inch of soft

water.

We shall now subjoin a Table of the Specific Gravities of a few Solids as well as Fluids, and afterwards a Table of the weight of a cubic inch of various substances in ounces Troy and Avoirdupois.

F F

The following examples will illustrate the use of these Tables.

EXAMPLE 1.

Required the weight of 10 cubic inches of wrought iron, in ounces Troy.

SOLUTION.

4.0313 weight of a cubic inch

Multiply by 10 number of inches

Product 40-313 oz. troy, Answer.

EXAMPLE 2.

The content of an iron chain, weighing 107 ounces avoirdupois, is required in cubic inches.

Tab.No: 4.4229)

SOLUTION.

Given Weight
107.0000

Quotient

(24.19 cubic inches required.

After the manner of the last example, the content in wine gallons of such incumbrances in a Distiller's Wash Still as cannot be exactly determined by the Problems in Mensuration, may at once be ascertained; but in treating of a Still, we gave another practical mode of finding the content to the greatest nicety. [See page 354.]

The easiest method of determining the Specific Gravity of any Fluid is by the Hydrometer, although some difficulty accompanies its use, owing to the change produced in the Specific Gravity of a Fluid. by difference of temperature.

As the strength of spirituous liquors is known by their Specific Gravity, and as the Specific Gravity of all Fluids is more readily ascertained by an Hydrometer than by any other means, it has been established by Act of Parliament that the HYDROMETER shall be the instrument employed by the Officers of the Revenue in finding the per-centage over and under proof of all spirituous liquors whatever. SYKES's Hydrometer, with copious directions for its use, and printed Tables, shewing the per-centage by inspection, may be had of MR. BATE, in the Poultry, Mathematical Instrument Maker to the Board of Excise.

There is likewise to be had an Hydrometer improved by CLARKE, and which many prefer to SYKES's.

USE OF THE HYDROMETER.

It has already been remarked that Fluids vary a little in their Specific Gravities by a change of temperature, and hence, as a difference in the Specific Gravity argues a difference in the strength, it is always requisite to use a THERMOMETER with the HYDRO

METER.

Also, in taking samples for trying the strength of spirits, it is necessary in Store-Pieces and large Vats, to make use of sinking vials, in order to get the sample from the middle of the liquor in the Piece or Vat, because a sample at the top may differ very considerably in strength from a sample at the bottom. In small vessels and Casks this difference is too trifling to deserve notice.

METHOD OF ASCERTAINING THE STRENGTH OF
SPIRITUOUS LIQUORS.

Let a Glass Tube be nearly filled with the liquor to be tried, and into the Tube introduce a THERMOMETER, with which agitate the liquor till the mercury becomes stationary: hereupon observe the temperature indicated, always taking the nearest degree, when the mercury rests between two degrees.

Next, wet the HYDROMETER up to the Cipher on the stem, in the sample to be tried; then chusing one of the hydrometer-weights, place it on the spindle, so as to rest on the lower bulb of the instrument. Returning the Hydrometer now into the sample, taking care to remove all air bubbles, press it gently down till the cipher on the stem is level with the surface of the liquor; after this, suffer the instrument to rise gradually and to assume a state of rest.

When the Hydrometer appears stationary, observe the sub-division on the stem corresponding to the surface of the sample. If the surface is not exactly at any division or sub-division, the nearest, mark on the stem under the surface must be considered the surface-mark.

The division corresponding with the surface of the sample is next to be added to the weight used, and the sum will be the Indication.

Then to find the strength by the Tables, look for the temperature given by the thermometer, and in the margin seek the Indication. Under the temperature,