In addition to the topographical sketch of the ground, each officer sends in a detailed report of its general character, its resources, and military capabilities. Each officer also makes a hasty reconnaissance of a road with a view to its employment as a military communication. All the information which can be obtained as to the character of the country through which it passes, and towns and villages near it, together with the construction, gradients, etc., of the road, are noted on the face of the sketch.
Fortification Branch.
Every officer is required, in this branch of the survey course, to design one or more works of defence for the occupation of a site, of which a contoured plan is furnished to him.
In performing this exercise the officer becomes, expert in reading the various forms and slopes of ground, as expressed by contours; he meets with and learns to provide for some of the many modifications of the conditions of defence which the occupation of irreglar sites necessitates, and he acquires facility in the application of descriptive geometry to the determination of the planes of defilade and the several planes of a work.
The data upon, which, the design, is framed consist of a plan of ground shown by contours and of some of the conditions to be filled by the proposed fortification, such as the objects for which; the site is occupied, the strength of the garrison, the extent, of the works, the nature of the defence of the ditches, the trace, or the, profile to be adopted, etc.
On the completion of his design the officer writes a report explanatory of the character of the works, he has adopted, and describing his arrangements both for the distant and near defence, with any improvements which have suggested themselves in working it out; and since the scale of the design, admits of considerable accuracy in its preparation, he is required to enter very fully into the detail of the arrangement he proposes.
The report is accompanied by tables showing how the remblai and deblai are equalized, and that the distribution of the latter is, economical.
Civil Applications.
Projects for a line of communication, general plan, and trial sections.—The officers are instructed in the general principles which should guide them in laying out lines of communication, whether by road, railway, or canal, and are then sent out to examine the country between two points five or six miles apart, and are required to decide on two or more routes which apparently offer the greatest facilities in point of gradients, soil, and the materials of construction. Availing themselves of the best map or plan they can obtain, they draw a plan showing approximately the divisions of the properties through which the trial lines are run; they then make trial sections; and from these sections and their previous examination of the ground, they determine on the line, to be adopted, embodying in a report a general description of the country, the obstacles encountered on each route, the gradients, curves, etc., and also the calculations which led to their decision. In their calculations they estimate the cost of the necessary constructions on each of the trial lines, the cost of conveyance for heavy goods on an assumed basis of daily traffic, and the time occupied in each case for quick transit.
Working plan and section.—A length of one mile of the route determined on as the best is selected, and for this a special survey is made, which is laid down as a working plan, the line being picketed out when no objection is made by the owners of the property through which it passes. A working section of the line is also prepared from accurate levels.