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The principal points for observation in a military sketch and report are―
ROADS. Their direction; nature; liability to injury; facility of repair; practicability, in what seasons, and for what species of troops; exposure to, and means of security from, enfilade; whether bordered or not by hedges, ditches, or banks, &c.
CANALS.-Means of destruction, or of rendering them of use; construction; depth of water, size of locks, &c.
RIVERS. Their sources, width, depth, velocity of current; fords for infantry and cavalry, whether permanent, or only passable at certain periods of tide, or seasons of the year, and if exposed to fire; means of passage; profile of banks; size and nature of vessels and boats employed in the navigation; tributary springs and rivulets; bridges, with their dimensions, materials, and construction, and means of destroying or repairing them.
MILITARY FEATURES.-Inclination of slopes, and all irregularities of ground; accessible or not for cavalry or infantry; description of country, open or inclosed; relative command of hills +; ravines; forests; marshes; inundations; barriers; plains; facilities for landing, if on a sea coast; military posts, and fortified towns, &c. STATISTICAL INFORMATION.-The population and employment of the different towns, villages, and hamlets, contained within the limits of the sketch. Agricultural and other produce; commerce; means of transport; subsistence for men and horses, &c.; with a variety of minute but important details, for which the reader is referred to the excellent essay on this subject, in the fourth volume of the “Mémorial Topographique et Militaire;" to the "Aide Mémoire des Officiers du Genie;" Macauley's "Field Fortification;" &c.
The degree of accuracy of which a sketch of this nature is susceptible depends upon the time that can be allowed, and the means that may be at hand. If a good map of the country can
* A ford should not be deeper than three feet for infantry, four feet for cavalry, and two and a half for artillery and ammunition waggons.-Macauley's "Field Fortification." The nature of the soil at the bottom should always be ascertained, and also if it is liable to shift, which is the case in a mountainous country.
If actual differences of level cannot be determined for want of time, still relative command may be obtained, and numbered 1, 2, 3, &c., accordingly.
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Me nstruments sed etcong round have ready been Muded a when tesenog ne noue ning in the detail between neasured nes neruar survey. In vidition to the kivantages zere scribed a ne zimuta compass, ir vill be bund jeentiarty veil uiarted or sketching a continuous ine, such as the course of a vau or iver, or line of coast, vinch reflecting ne ingres vita he magnetic meridian, measured by the compass, can be read off with quite as much tccuracy is they can be laid lown by the smail protractor used in the held. This should have a scue of 3, 4, or 3 inches to one mile OF "VIatever other proportion may be preferred) engraved on the other beveiled side, and with a sketching portzelo and compass, ogether with a smail sextant and feid telescope, comprise all the instruments that can be required by an officer
The present * Sabretache” is of ittle sen horsebacks, and on foot it is a mere incumbrance. It s most tesirable that Officers of 3ngineers, and those attached to the Quarter-Master-General's department. m service, should be equipped with one of an improved pattern, which might easily be arranged so as to answer for a portfolio and sketching case, and at the same time contain much scales and irawing instruments as are required by an officer employed upon an extensive reconnaissance.
employed on a reconnaissance; and as they can always be carried without inconvenience about his person, or strapped in front of his saddle, he need never be driven to the necessity of sketching entirely without their assistance, though the practice of doing so occasionally is decidedly of service, as it teaches him to make use of his eyes, and tends to make him a good judge both of linear and angular measurement *.
Sketching such parts of the interior detail as have a decidedly marked outline is comparatively easy, but the delineation of ground, so as to represent the various slopes of the hills and irregularities of the surface, is far more difficult; and methods have been adopted both on the Continent and in this country, as systems for expressing these features, giving not merely a general idea of their character, but a mathematical representation of their various complicated inclinations; so that the angle of every slope might be evident from a mere inspection of the drawing, or measured from a scale; and, consequently, furnishing data for constructing sections of the ground in any required direction. This degree of perfection would of course be most desirable in military sketches, as well as in finished topographical plans, but the labour and difficulty attending the execution will always prevent its general application, excepting in surveys of a national character, or of limited detached portions of ground.
The two methods in general use for representing with a pen or pencil the slopes of the ground are known as the vertical and the horizontal. In the first of these the strokes of the pencil follow the course that water would take in running down these slopes; in the second (which is comparatively of late introduction) they represent horizontal lines traced round them, such as would be shown on the ground by water flooding the country at the different stages of its progressive altitude. This last is the mode now generally practised, and it certainly produces a more correct re
* A protractor (for want of a better) can be made by folding a square or rectangular piece of paper into three, which, when doubled, divides the edge into six portions of fifteen degrees each; these can be again divided into three 15 parts, by which angles of five degrees can be laid down, or even approximately observed, the intermediate degrees being judged by the eye.