I always think that engineers should uniformly work in S.I. Units to avoid confusion. These measurement explanations make our present-day measurements look positively uniform, easy and clear.

Let's see. A statute mile, a sea mile, a Scottish mile, an Irish mile, a chain, a perch, an ell, a fall and how about those roods...

**Rankine, William John MacQuorn,**

*A Manual of Civil Engineering*, Exeter Street, Strand, London, Charles Griffin and Company, 1883.**Measures of Length.--**The standard measure of length established by law in Britain is the

**yard**, being the distance, at the temperature of 62 degrees of Fahrenheit's thermometer, and under the mean atmospheric pressure, between two marks on a certain bar which is kept in the office of the Exchequer, at Westminster.

In addition to the yard, the following units of length are employed for purposes of civil engineering in Britain:--

The

**Inch**, one thirty-sixth part of the standard yard; with binary, decimal, or duodecimal subdivisions.

The

**Foot**, one-third part of the standard yard; with decimal or duodecimal subdivisions.

The

**Fathom**of two yards.

The

**Chain**of 66 feet or 22 yards; divided into four

*poles*of 5 1/2 yards, and 100

*links*of 7.92 inches.

The

**Statute Mile**of 1,760 yards = 5,280 feet = 80 chains, divided into 8

*furlongs*. To these may be added, in cases of harbour engineering--

The

**Nautical**or

**Sea Mile**, being the length of one minute of a degree of latitude at the mean level of the sea. The length of this mile varies in different latitudes, from about 6,107 feet at the poles to about 6,045 feet at the equator, its mean value being nearly 6,076 feet, or 1.1508 statute mile. A value commonly taken for the nautical mile is that of a minute of longitude at the equator, or 6086 feet - 1.1527 statute mile. The nautical mile is sometimes subdivided intp 10

*cables*, and 1,000

*fathoms*; the fathom thus obtained being, on an average, about 1/80th longer than the common fathom.

Amongst obsolete measures of distance the following may be mentioned, as they occasionally occur in old plans:--

The Irish

*Perch*of 7 yards, being greater than the imperial perch in the proportion of 14 to 11.

The Irish

*Mile*of 320 Irish perches = 2,240 yards = 6,720 feet, bearing to the statute mile the same proportion of 14 to 11.

The Scottish

*Ell*of 37.06 imperial inches.

The Scottish

*Fall*of 6 ells, or 18.53 imperial feet.

The Scottish

*Mile*of 1,920 ells = 5929.6 feet.

Each of these miles is divided, like the statute mile, into 8 furlongs, and 80 chains, so that the Irish, Scottish, and imperial mile, furlong, and chain, bear to each other the proportions--

6720 : 5929.6 : 5280

1.27 : 1.123 : 1.000

The French measures of length are all decimal multiples and submultiples of the METRE, which is approximately one ten-millionth part of the distance from one of the earth's poles to the equator. The value of the metre in British measures is

3.2808693 feet, or 39.37043 inches.

**Kilometre**of 1,000 metres, or 3280.8992 British feet, is 0.621383 of a statute mile.

For further information of the same kind, see the Comparative Table of French and British Measures at the end of the volume.

*****

The

**Measures of Area**used in British civil engineering are--

The

**Square Inch**.

The

**Square Foot**of 144 square inches.

The

**Square Yard**of 9 square feet.

The

**Acre**of 10

*square chains*, or 100,000

*square links*, or 4,840

*square yards*, subdivided either decimally, or into 4

*roods*of 1,210 square yards, and 160

*perches*of 30 1/4 square yards.

The

**Square Mile**of 640 acres, or 3,097,600 square yards, or 27,878,400 square feet.

The Irish

*acre*, subdivided into 4

*roods*and 160

*perches*, and the Scottish

*acre*, subdivided into 4

*roods*and 160

*falls*, bear to the imperial acre proportions which are the squares of the proportions borne by the Irish and Scottish miles respectively to the statute mile; that is to say,

Irish acre : Imperial acre : : 196 : 121 ;

Also, Irish acre : Scottish acre : Imperial acre

: : 1.6198 : 1.2612 : 1.0000 nearly.

The

**Measures of Volume**used in British civil engineering are--

The

**Cubic Inch**.

The

**Cubic Foot**of 1,728 cubic inches.

The

**Cubic Yard**of 27 cubic feet.

In the engineering of water-works, the

**Gallon**is used in stating quantities of water. Its statutory value is

277.274 cubic inches, or 0.16046 cubic foot;

but it is convenient in calculation, and in general sufficiently accurate for purposes of water supply, to use the approximate values,

One gallon ...= 0.16 cubic foot, nearly; and

One cubic foot= 6 1/4 gallons, nearly.

Other special measures of volume are employed for certain kinds of materials and work; but these will be explained further on.

***Comparative Table of French and British Measures.**