A Second Experiment in Ecological Surveying. 203 
resorting to the use of the optical square. After salient points are 
marked the actual boundaries can be rapidly drawn by eye with 
considerable accuracy. Meanwhile detailed notes are made on the 
vegetation included in the square, and representative plants are 
collected, labelled, and pressed. 
In this way a map of the whole area was constructed in sections 
on a scale of and a detailed record of the vegetation obtained. 
This map is now being put together and reduced. 
As has been indicated above, the halophilous vegetation of the 
Bouche d’ Erquy is evidently closely dependent on very slight 
changes of level, and these changes constantly occur in the course 
of a few feet or even of a few inches. It therefore became desirable 
to map certain characteristic portions of the area on a larger scale 
than that adopted in the general map. This was done by means of 
the “gridiron” method, which essentially consists in taking a 
25-foot square, laying tapes on every side, and also laying four 
other 25-foot tapes across the square parallel to the sides, at inter¬ 
vals of 5 feet. A plan is then constructed on squared paper, as in 
the method of squares, but on a scale of Details correct to 
less than 6 inches can be mapped on this plan with great rapidity, 
since the surveyor can always stand immediately over his work. 
Levels are then taken with a telescope and levelling staff reading 
to T 4 0 -foot, wherever desired, so that contour-lines T ^-foot apart, 
which are of great importance in attempting to understand the 
distribution of the vegetation, can afterwards be constructed. A 
full account of the “gridiron” method will appear in an early 
number of this journal. 
A great deal of time and thought was spent on the organisation 
of the work of surveying, and it was most satisfactory to find in the 
field that this labour was by no means thrown away. It would 
indeed have been impossible to get through the work without the 
careful organisation employed. The party consisted of about 
twenty-seven persons, mostly from University College, but with 
representatives from Cambridge and from the Royal College of 
Science. The bulk of the party was divided into five working 
sections of three members each, who undertook respectively the 
duties of Surveyor, Diarist, and Collector, the Diarist and Collector 
helping the Surveyor when necessary. To each section a given 
area was assigned, after the preliminary work of constructing a 
base-line with the necessary perpendiculars and parallels, and of 
ranging the squares, was completed. The rest of the party formed 
the Staff, and its members undertook this preliminary work together 
with the general direction of the detailed survey, as well as the 
earth-boring, levelling, salt-estimations, photographing character- 
