[123] The Standard Temperature was 31°.24, which not being exactly 1 Quarter, another Decimal is added, (for Ease in Computation,) by which 31.24 becomes 31.25, i. e. by dividing one Degree of Heat into 100 Parts, and taking 25 of those Parts, or dividing the 100 by 25, the Answer is 4, i. e. 1⁄4 of the whole 100: or (31)​1⁄4.

[124]

The Foundation of the fourth Table.

(Ph. Tr. for 1777, Part 2d, Pages 564, and 566,)—From the Mean of a Series of Experiments with a Manòmeter, or Instrument to measure the Rarity and Density of the Atmosphere, depending on the Action of Heat and Cold, it was found, that when the Portion of a Tube containing Air (at the Temperature of freezing by Farenheit, and Pressure of 30​1⁄2 Inches[125] by a common Barometer) was divided into 1000 Parts; the Volume of Air within it, encreased nearly in a certain Proportion, as each Degree of Temperature encreased; viz. at a Mean, 2.43, or simply (by rejecting the 2d Decimal as too minute) 2.4: that is, a 1000 Parts of Air became by Expansion with one Degree of the Thermometer, equal to 1002.43: i. e. the Portion of Air occupying 1000 Parts, did, with the Addition of one Degree of Heat, occupy 1002.43 Parts: that is (by rejecting the 2d Decimal 3 as too minute) occupied two Parts and 4 Tenths more than the thousand.

Construction of the fourth Table.

Supposing therefore that the Portion of the Tube containing Air, was one Foot in Length of Height, divided also into a thousand Parts; one Degree of Heat would encrease or expand it two Parts and four Tenths more than the thousand Parts into which the Foot was divided.

CAUTION.

The fourth Table properly consists of only nine horizontal Columns of thousands, in Breadth; which Columns are extended in Length to one hundred Lines, corresponding to 100 Degrees of Heat.

The Table is here divided, in order that it may conform to the Size of the Pages: by which Means the Formation of each vertical Number by the following Rule, (which renders the Table self-evident) might without this Caution, have been attended with some Difficulty.

The vertical Columns below the Figures expressing each thousand, shew the Expansion of Air on each respective thousand, with the corresponding Degrees of Temperature indicated by the Thermometer in the vertical Column to the left Hand.