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SHADING AND ENGRAVING TOPOGRAPHICAL PLANS.
The other system of supposing the light to fall obliquely upon the ground (as in nature), either at one fixed angle or at an angle proportioned to the general character of the slopes *, is decidedly favourable to the talent of an artist; but there are two objections its general adoption in plans of an extended survey: first, the difficulty of execution; and secondly, its ambiguity, even when correctly drawn, except to those accustomed to the style. The slopes directly opposed to the light would evidently receive a greater portion of illumination than the summits of the highest hills; and, in fact, the whole arrangement of the disposition of the shades is quite different from what it would be under a vertical light, as is seen by exposing a model of any portion of ground to a strong light from a partially-closed window. The practice of copying the effects of light and shade from models is the best introduction to this system of shading ground, and is in fact indispensable before attempting to finish a plan t.
The method now most generally practised in topographical plandrawing partakes of both these systems $; the light is considered as falling nearly vertical, but sufficiently oblique to allow of a decided light and shade to the slopes of the hills, trees, &c. The hills are shaded, not as they would really appear in nature, but on the conventional system of making the slopes darker in proportion to their steepness; the summits of the highest ranges being left white. This arrangement, though obviously incorrect
* Mr. Burr proposes an angle of about 150 for a flat country, and 40° for mountainous districts; the angle of oblique light ranging between these two extremes according to the nature of the ground.
+ Mr. Dawson, whose talents and energy have done so much towards bringing the sketching and shading plans of the Ordnance Survey to the present state of perfection, was the principal advocate of this system of oblique light; and some of the copies, from models of large tracts of country drawn by Mr. Carrington, at the Ordnance Map-office, in the Tower, are hardly to be distinguished from the models themselves, when they are both placed in the proper light.
# These and the preceding remarks apply solely to shading with the brush ; the methods of delineating slopes by the pen and pencil having been explained in the last chapter. The Ordnance Surveys of the North of England are finished on this system for the engraver, even though the ground may have been instrumentally contoured. These maps, however, are at present engraved upon the same scale as those of the old surveys of the southern counties, 1 inch to 1 mile, though plotted upon that of 6 inches, in order to have the whole maps of England uniform in scale and in execution.
SHADING AND ENGRAVING TOPOGRAPHICAL PLANS.
in theory, has the advantage of being generally understood even by those not accustomed to plan-drawing, and is also easy of execution : it is that now adopted in finishing the plans of the Ordnance Survey, and from which the features of the ground are engraved on the vertical system of etching, as being much the easiest, although not so for sketching in the field.
Trials have also been made to render the patent process of engraving by a machine, known by the name of “Anaglyptograph,” which answers so beautifully for giving a correct representation of a cast, or basso-relievo, available for topographical designs. A surprising relief is produced by this method of engraving, but it renders the general surface of the plan so dark as to obscure the accuracy of the outline; and as it is necessary that a model should be previously made of the feature to be represented, it is only suited to small portions of irregular ground.
Attempts have likewise been lately made to introduce some system of engraving that may combine as far as it is possible the accuracy of horizontal contours with the effect of etching, which it is hoped will before long be brought into practice.
In finishing detailed plans on a large scale, stone or other permanent buildings are generally coloured red (lake or carmine). Wooden or temporary structures are tinted with a shade of Indian ink. Water is always coloured blue. Where distinctions between public and private buildings or property are required to be shown, different colours must be used and explained by references on the drawing; the same remark applies to the distinction between buildings erected and those only contemplated. The most usual conventional signs have already been alluded to in pages 68 and 69.
The preceding chapters will, it is believed, be found to contain all necessary information connected with the survey of any tract of country, whatever degree of accuracy or detail may be required; but in a newly-established colony, or one only partially settled, the primary object in view, in commencing an undertaking of this nature, is not the same as in that of a thickly peopled and cultivated country. In the latter case, the surveyor aims at obtaining, by the most approved methods consistent with the time and means at his disposal, data for the formation of a territorial map showing the position and extent of all roads, towns, provinces, counties, and, where the scale is large, parishes, and even the boundaries of property and cultivated or waste land; as well as the features of the surface of the ground, and all natural and artificial divisions, together with the collection of a variety of other useful geological and statistical information. In a new country only the natural lines and features exist;—the rest has all to be created.
The first operations then, required in a perfectly new settlement, are, the division into sections of such size as may be considered best adapted to the wants of settlers, of the land upon which they are to be located; and the marking out the plan of the first town or towns, the sizes and positions of which will of course be regulated by local circumstances and advantages; whilst the first rural sections will naturally be required either in their immediate vicinity, or contiguous to the main lines of communication leading to the different portions of the province, whose local importance is the earliest developed.
In the case of a small settlement established upon the coast of any country, for the immediate reception of settlers who require to be put in possession, directly upon their arrival, of a certain stipulated amount of land for agricultural or other purposes, the simplest form of survey must necessarily be adopted; that described in Capt. Dawson's Report upon the Survey of New Zealand for instance, which consists simply in marking methodically upon the ground the angles of a continued series of square or rectangular figures, leaving even the roads which are intended to surround each block of sections, to be laid off at some future period,—would answer the purpose of putting impatient emigrants in possession of a homestead containing about the number of acres to which they might be entitled. But this system could not be carried out extensively with any degree of accuracy, even in a comparatively level country, and not at all in a mountainous or irregular one. In fact, it is not a survey; and though perhaps it may sometimes be necessary to adopt what Mr. F. Wakefield, in his recently-published pamphlet upon Colonial Surveying, terms this “make-shift process,
,”* the sooner a regular survey takes its place the better for the colony, even on the score of the ultimate saving that would be effected by getting rid of the necessity of incessant alterations and corrections; to say nothing of the amount of litigation laid up in store by persevering in a system necessarily entailing an incorrect division of property, upon which there is no check during the progress of the survey, and for which there is no remedy afterwards.
Excepting in some isolated instances such as described above, where everything is required to give way to the imperative necessity of at once locating the first settlers upon land for which payment has been received, (for, by the present system of colonization, no land is alienated from the Crown otherwise than by purchase, the greater portion of the proceeds of the sale being devoted to the purpose of further emigration,) the first step to be undertaken at the commencement of the survey of a new country, is a careful and laborious exploration within the limits over which its operations are to extend ; during which would be collected for subsequent use a vast amount of practical information
* For an explanation of the details of this species of surveying, see Mr. Kingston's Statements, page 33, Third Report of the South Australian Commissioners, 1838 ; and Captain Dawson's Report on the Survey of New Zealand, 1840.
as to the number and physical condition of the aboriginal natives (if any); the geological character of the soil; its resources of all kinds; sources and directions of rivers; inland lakes and springs; the probable sites of secondary towns; the most apparent, practicable, and necessary main lines of communication; prominent sites for trigonometrical stations, &c., &c. A sketch of the country examined, rough and inaccurate doubtless, but still sufficient for future guidance, is at the same time obtained; the positions of many of the most important points for reference being determined by astronomical observation, and the altitudes of some of them by the mountain-barometer or aneroid, or by the temperature of boiling water, by methods already explained.
The next step should be, if this question has not been already determined by strongly-marked local advantages, or previous settlement, the position of the site of the first principal township, a nucleus being immediately required where fresh arrivals may be concentrated, prior to their dispersion over the country. The size * and figure of the town will of course vary according to circumstances; and the principal general requirements that should suggest themselves to any one charged with a decision of this nature are,—facilities of drainage; plentiful supply of good water; easy access both to the interior of the country, and, if not situated on the coast, to the adjacent port; the apparent salubrity of the site; facility of procuring timber and other building materials, such as sand, lime, brick-earth, stone, &c.; security from predatory attacks, and vicinity to sufficient tracts of land suited to agricultural and pastoral purposes.
The site of the town, with its figure and extent, being decided upon after a careful investigation of the above and a variety of other minor considerations, the best main lines of road diverging from it in all the palpably-required directions should be marked out, and upon these main lines should abut the sections to be first laid out for selection. Errors of judgment will doubtless be subsequently found to have been made in the directions of some of
* The size of the lots into which the township is to be divided may vary from a quarter of an acre to one acre; half an acre would be found generally sufficient. It is customary to give to the first purchasers of rural sections one town lot in addition for every such section, the remaining lots to be sold either by auction, or at some fixed price.