APPENDIX.

699

Hot liquids should be allowed to cool, or, if it be necessary to observe theirspecific gravity at elevated temperatures, a comparative trial should be madeon the liquid while hot, and on a portion when cold, so that the indicationmay be corredted. If it be needful to take the specific gravity of any liquidcoming under the heads b, c, and d, a gallon should be accurately weighed.

In chemical, dye, and print works, where hydrometers are placed in thehands of foremen for frequent use, they should be regularly brought at somestated time to the laboratory for verification.

Thermometer Scales.

To convert Centigrade (Celsius) into Fahrenheit .—If the temperature beabove the freezing-point of water (32 0 F. = 0° C.), multiply by g, divide by 5,and add 32 to the quotient. If it be below freezing-point (32 0 F. = o° C.),but above o° F. (= -18 0 C.), multiply by 9, divide by 5, and subtradt the resultfrom 32 0 . If below —18 0 C. (= o° F.), multiply by g, divide by 5, and sub-trad): 32 0 from the result.

Reaumur’s scale, in which the boiling-point of water is made 80°, and thefreezing-point, as in the Centigrade, o°, is still used in many German dye andprint works.

To convert Reaumur into Centigrade , whether above or below freezing-point,multiply by 5 and divide by 4.

To convert Centigrade into Reaumur , multiply by 4 and divide by 5.

To convert Reaumur into Fahrenheit , or vice versa, the rules above given forthe conversion of Centigrade into Fahrenheit, &c., will apply, 4 being usedrespectively as multiplier or divisor instead of 5.

Decimal or “ Metric ” Weights and Measures.

Measures of Length.

Millimetre = 0-03937 inch.

7 Centimetre = 0-393708 ,,

Decimetre = 3'937°79 inches.

Metre = 39 370790 inches.

,, = 3-2808992 feet.

„ = 1-093633 yards.

Decametre = 32-808992 feet.

Hedtometre = 328-08992 ,,

Kilometre = 3280-8992 „

„ = 1093-633 yards.

Myriametre = 10936-33 „

,, = 6-2138 miles.

English inch = 2-539934 centimetres.

,, foot = 3-0479449 decimetres.

,, yard = 0-91438348 metre.

,, fathom = 1-82876696 metres.

„ furlong = 201-16437 ,,

„ mile = 1609-3149 „

Superficial Measures.

Square millimetre = of a square inch.

,, „ = 0’00I55 n >>