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Main Ditch, in order that the face of the Bastion may defend it more effectually than could have been the case were they both of the same depth. The ditch of the Reduit is still more diminished, in order to facilitate the communication between it and the Demilune. Beyond these ditches is a space of level ground, thirty feet in breadth, extending round the Fortification, called the Covered way, and protected by a parapet eight feet in height, the superior slope of which forms a gentle slope towards the country, terminating at a distance of from sixty to ninety yards, called the Glacis.

We have thus given an outline of the principal works and general plan of a Fortification: there are, however, many other works employed to strengthen and improve the defence; these we have described under their several heads.

The construction of a Field Work is not in general so perfect as in Permanent Fortification, its object being obtained, less from the regularity of its shape, than from the skill evinced by the Engineer in its tracing and relief. Every species of material may be advantageously employed in the construction of Field Works, and as the period of time during which they are occupied is often limited to twenty-four hours, but few implements are required for raising them, save the pickaxe and shovel, which are the only means that are always at hand. The principal of these works are Redans, or Flêches, Redoubts, Têtes, or Têtes du Pont, Field Forts, and Lines continued or interrupted; and as these are severally explained in their proper places, nothing more remains, but to mention a few of the general rules or maxims by which Engineers are guided in their construction. 1. A Salient angle should not be less than 60°, especially when it is undefended by a flanking fire; as its area then becomes too contracted for the purpose of a good defence, besides presenting a large dead angle in its front, which increases in proportion as the Salient angle diminishes.

2. The Sa

lients, which are the points most exposed, should, if possible, be directed towards some natural obstacle, which will prevent the Enemy from approaching them, on the prolongation of their Capitals. 3. The angle formed by one work flanking another, should never be less than 90°, nor should it exceed that angle more than is necessary. 4. The

90

FRENCH MEASURES.

length of the lines of defence ought not to exceed eighty Toises at most.

In erecting Field Works of importance, a regular tracing is made, by means of pickets, cut down for the purpose, and the proper dimensions being given by the measuring tapes, the profiles are formed by larger pickets, connected with each other by cords and lines, kept for this purpose. The method of tracing on the ground differs but little from the usual manner of tracing on paper, excepting that strings, pickets, and the edge of the spade, are substituted for the ruler and pencil. Vide Systems.

FORWARD. A word of command, given when troops are to resume their march after a temporary interruption. FOSSE'. A ditch.

FOUGASS. A small mine from six to eight feet under ground. Fougasses may sometimes afford a good defence to Field Works, not on account of the destruction which they may cause to the Assailants, as this is generally inconsiderable, but because they tend to damp the ardour of their soldiers, and throw them into confusion.

FRAISES. Palisades, when ranged in an inclined position, and on slopes pointed to the breasts of the Enemy, are called fraises. Vide Palisades.

FRENCH MEASURES. The new French Measures frequently occur in Maps and Plans, and being a subject of interest to Military Men, a few Tables are annexed, which, it is hoped, may prove useful.

In 1788, the General States in France directed their attention to remedying the great defects arising from the system of measures then in use, which, from their total want of uniformity, were found to cause much confusion in Mercantile affairs. After due consideration, it was decided, to adopt the ten millionth part of the fourth part of the Meridian, or of the quadrant comprised between the North Pole and the Equator, for the unit of the new measure of length, and that all others should be calculated from this Standard. In order to ascertain the value of the unit, it was determined that an arc of the Meridian should be actually measured. The result of this operation ascertained that a quadrant of Meridian, lying between the North Pole and the Equator, measured 5,130,470 Toises, or 10,936,578 English yards; and the ten millionth part of

this quantity, which was to form the standard unit, was therefore equal to 1.093578 English yard.

This unit was denominated a Mètre; the words deci, tenth of; centi, hundredth of; milli, thousandth of; being prefixed to the word expressing the unit, served to denominate the subdivisions; and the words deca, ten; hecto, one hundred; kilo, one thousand; myria, ten thousand; expressed the multiple of the unit.

1st. Long Measure.

The unit of the long measure, used for measuring cloth, linen, &c., is the mètre; it is divided into 10 decimètres, each of which is equal to 10 centimètres, and each centimètre to 10 millimètres.

1 Mètre

1 Decimètre =

1 Centimètre =

French into English.

3.3.370 Eng. ft. & in. = 3.0784 Old. Fr. ft. 3.937 do. inches = 3.6941 do. in.

Imperial Measure.

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English into French.

1 Inch (of a yard) = 2·539954
1 Foot (of a yard) 3·0479449
1 Yard, Imperial
0.91438348

French Centimètres.

do. Decimètres. do. Mètre.

2d. Itinerary Measure. Distances are expressed by myriamètres (10,000 mètres), and kilomètres (1000 mètres). There are four measures by which distances are reckoned in France. 1st. the lieue de poste, to regulate the charges on travellers. 2d. the lieue marine, twenty in the degree, adopted by Geographers. 3d. the lieue commune, twenty-five in the degree. 4th. the lieue moyenne.

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French into English. Toises, (old measure.) mètres. 2000 = 3898

20 in the degree.

Lieue communie,
25 in the degree. f

Lieue moyenne

=2850

Eng. yds. ft. in.

= 4262 26

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2280 4443.80 48,59 0 4

= 2565 = 5000 = 5470 English into French.

1 Fathom (2 yds. Imp. Meas.) = 1 Pole, or Perch (54 yds.) =

1 Furlong (220 yds.)

1 Mile (1760 yds.)

1.82876696 Fr. mètre. 5.02911 mètres. 201·16437 mètres. 1609 3149 mètres.

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FRENCH MEASURES.

For the measurement of Carpentry and Masonry, the French still use the Toise, which is now fixed at 2 mètres exactly, making an increase of 2 per cent. on the "toise of Paris." The toise is divided, as formerly, into 6 feet, each foot into 12 inches, and each inch into 12 lines.

1 Toise 2 mètres 6 ft. 6·42 in. English. 3d. New French Division of the Circle.

100 Seconds = 1 min. of space, each sec. = 10 mètres. 100 Minutes = 1 deg.

100 Degrees = 1 quadrant

4 Quadrants, or 400 degrees = = 10,000,000 mètres.

each min. 1000 do. each deg. 100,000 do. 1 circle, each quadrant

4th. New French Division of Time.

100 Seconds 1 minute.

100 Minutes = 1 hour.

10 Hours = 1 day.

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The Old Division, which is the same as the English Measure, is however the one in general use.

5th. The unit of Land Measures is a square, each side of which is 10 mètres in length, and called an Are; it is divided into 100 parts, called Centiares, each consisting of a square mètre.

A larger measure, consisting of 100 ares; each side of this square is 100 mètres in length. This measure is termed a Hectare.

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1 square Yard

1 Rod (sq. perch)

1 sq. yard 1.76 foot. English into French.

=

1 Rood (1210 sq. yards) = 1 Acre (4840 sq. yards) =

0.836097 French sq. mètre. 25.291939 French sq. mètres. 10·116775 ares. 0.404671 hectares.

6th. Rules for finding the Value of the preceding Five Measures.

To convert French mètres into English feet. Multiply the mètres and decimals by 3.28.

To convert French mètres into English yards. Multiply the mètres and decimals by 1.09.

To change the new degrees and minutes into the old

division.

Subtract one-tenth, and find the value of the Remainder by the Rule of Reduction.

The French new method of fixing a scale to their maps, is by making it some definite fraction of the whole, as Toooo, Tooooo. To reduce this into the common English measure, divide 63360, the number of inches in one mile, by the denominator of the fraction. Thus a scale of too, will be converted into a scale of 3.168 inches to a mile.

7th. The Solid or Cubic Measure.

The measure in use for the sale of timber is called Stère, and is a cubic mètre.

The stère or cubic mètre
The decistère

8th. Measure of Capacity.

35.317 English cubic feet. the tenth of a cubic mètre.

The unit of this measure is the litre, equal to one cubic decimètre. The decalitre contains 10 litres, and the hectolitre 100; the kilolitre is equal to one cubic mètre, or 1000 cubic decimètres.

1 Litre

= 1.761 English pint.

1 Decalitre = 2·201 Eng. galls. = 1 Hectolitre 22.010 Eng. galls.

10 cubic decimètres. 100 cubic decimètres.

The measure still used for the sale of corn, coals, salt,

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1 Quarter (8 bushels) =

36.347664 litres.

1.09043 hectolitre.

2.907813 hectolitres.

1 Chaldron (12 sacks) = 13.08516 hectolitres.

9th. The unit in weighing is the kilogramme, equal to the specific weight of the distilled water contained in one cubic decimètre.

The kilogramme has been found, by repeated experi

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