370 



SCIENCE OF GARDENING. 



Part II. 



the kitchen-departments generally rise on each side of the walks ; and in large parterres, 

 one of the chief beauties arises from the inequalities of the surface. The depth of ponds, 

 excavations for dung, earth, &c. ridges, hot-beds, rock works, even houses, trees, &c. are 

 all to be measured with reference both to their horizontal and perpendicular extensions. 

 Four persons are required in performing such operations accurately ; two to hold the 

 chain or line in a horizontal position, or in the plane of the general surface ; one to take 

 the dimensions downwards or upwards from this with the measuring-rod, and one to mark 

 down the dimensions. 



1 900. In protracting elevations and depressions on paper, the simplest way is to introduce 

 sections, in dotted or otherwise distinguished lines, to prevent their being mistaken for 

 surface-lines ; or in wavy surfaces, figures may be introduced, thus "5 or 4, to denote their 

 elevation above, or depression below, some piece of water, or other surface fixed on as a 

 medium. Some excellent observations on this subject will be found in Major Lehman's 

 Topographical Plan Drawing, as translated by Lieutenant Siborn, (oblong fol. Lond. 

 1822,) which it is to be hoped will soon be appropriated in the popular books on land- 

 surveying, and adopted in practice. 



1901. Where it is in contemplatio?i to form pieces of water, the elevations and depressions 

 or levels must be taken and recorded either by sections or arithmetically with the greatest 

 accuracy ; and, in some cases, sections may require to be taken to show particular trees, 

 buildings, the depth of water, or other objects. (Jig. 349.) 



1 902. With respect to the elevations and shapes of hills and mountains which may lie 

 within parks or plantations, they are only to be measured correctly by the quadrant and 

 theodolite, in the hands of regular land-surveyors ; and, therefore, are not considered as 

 here included. Their shape and dimensions are laid down in maps in the same manner 

 as those of smaller deviations from the flat surface. Inaccessible dimensions of height, 

 as of trees or buildings, are obtained by the quadrant, or by relative comparisons of 

 shadows ; of depth, as of water or wells, by rods ; of breadth or length, by finding the 

 two angles of a triangle whose base shall be in one extremity of the distance ; and apex 

 in the other. These, and many other equally simple problems in trigonometry, need not 

 be enlarged on, because they must be supposed to form a part of general education. 



1 903. The greatest accuracy is requisite in transferring plans of garden-scenery. Not 

 only the mere ground-lines are to be transferred ; but to form a complete plan, the 

 distances between scattered trees or trees in rows, or otherwise regularly disposed, ought 

 to be marked, the situations of their stems indicated, and, where they are of considerable 

 size, representations of the horizontal extension of their heads (Jig. 350. b) should also be 

 given. The same ought to be done in the case of walls, buildings, and all other raised ob- 

 jects. The intention of a ground-plan is to give an idea of the superstructure ; and with- 

 out such additions as these and others of a pictorial nature (fig- 350.), to the mere 

 ground-lines, that idea must be very imperfect, at least in plans of mixed scenery. 



1904. For protracting rural objects various modes have been adopted by land-surveyors : 

 trees are sometimes shown by small crosses or ciphers, triangles or dots (Jig. 350. a) ; by 



%. 350 



& |g 



an orbiculate line representing the extension of the branches or head, and a dot in the 

 place of the trunk (a and e) ; by the same, with the addition of a shadow, taken when the 

 sun is south or south-west, and his elevation exactly 45, by which the points of the com- 

 pass are readily ascertained throughout the plan, and the shape of the head, and the height 

 of the tree exhibited (e) ; sometimes an elevation or profile of the tree is given, either 



