202 A Second Experiment in Ecological Surveying. 
and level the physical features and the plant-associations of the 
area, while concurrent work was to be carried on upon the nature 
and wetness of the soil, salt percentages, etc. It will be seen that 
the area presents great attractions to the botanical cartographer. 
The plant-associations are very well marked, and, with the exception 
of the comparatively slight influence produced by the grazing of a 
few sheep and cattle, is practically untouched by human agency. 
The surface dries rapidly enough to make it easy to walk about 
upon except during the few hours per month when it is actually 
covered by the tide, and the differences of level, while of great 
importance to the distribution of the associations, are not great 
enough to put difficulties in the way of the actual work of surveying. 
It was originally intended to work on the lines of an ordinary 
land survey, but after various preliminary field experiments near 
London, it became clear that some modification of this method was 
very desirable. The problem being to map the details of complicated 
areas of vegetation, ordinary survey lines and off-sets become 
unworkable; for either the number of lines has to be multiplied to 
an impracticable extent, or the individual off-sets have to “pick up” 
so many boundaries that confusion inevitably results. 
The solution was found in the “method of squares.” A con¬ 
venient base line is taken, as in an ordinary land survey, and upon 
this rectangles are constructed on each side so as to enclose the 
whole of the area it is desired to map. Flagged sticks are placed 
at intervals of 100 feet along the base line and along the sides of 
these rectangles. The whole area of each rectangle is then plotted 
out into squares with sides of 100 feet each by placing other flagged 
sticks at intervals of 100 feet each way, and this is done by simple 
ranging against the flags of the base line, perpendiculars, and 
parallels. 
The work of mapping now begins. The party is divided into 
several sections to each of which one or more rectangles is allotted. 
o 
Each surveyor is provided with a field-book consisting of leaves of 
squared paper, and each 100 foot square is mapped on a single leaf. 
The physical features are put in first and then the boundaries of the 
different plant-associations, those which are to be recognised having 
been previously agreed upon and designated by symbols. Any point 
within the square can be at once identified in the map by means of 
imaginary perpendiculars dropped from known points on the sides, 
so that the surveyor, by standing at the point he wishes to mark, 
can get two assistants to fix his position by optical squaring from 
the side lines. In practice, by placing sticks at intervals of 20 feet 
along the side lines before he begins to map, the surveyor can soon 
judge his position in the square with sufficient accuracy, without 
