GRADES, LEVELS, CONTOUBS 53 



even though it does not stay on one plane all 

 the time. But to work out a plan for grounds of 

 irregular surface, the irregularities must be con- 

 sulted and set down upon the drawing; other- 

 wise the plan cannot fit. It is, therefore, a little 

 less simple to design such a garden, and a topo- 

 graphical map is essential as a basis to work 

 upon, if any great irregularities exist. 



This is getting rather too deep into techni- 

 calities possibly for the average amateur; yet 

 a contour map is a very simple thing, easy to 

 understand and easy to work upon — and not 

 indeed very difficult to make, although I shall 

 not ask you to go quite as far as that. For an 

 engineer's survey should be made of land that 

 varies enough to affect house and garden de- 

 sign; then all the work can be planned exactly. 

 Such a survey reckons usually from a level pre- 

 viously determined by the general survey of the 

 town or county, but this does not matter. All 

 that matters is the mark of the lowest level, 

 which will be the lowest figure given, whatever 

 the situation may be. This mark may be or 

 anything else; but everything that is not on its 

 level will be above it. 



Contours at one foot ascend from this lowest 

 plane a foot at a time; that is, imagining the 

 land under survey to be submitted to an inun- 



