THE RAPID SURVEY OF AN ESSEX SALT-MARSH 295
Glen Works, Hoddesdon, Herts., and cost about 15 shillings
each.
(b) The level. Acccurate levelling is essential, but a suitable
substitute for the usual Dumpy or Precision level was avail-
able. This was an ex-W.D. Artillery Director which, com-
plete with tripod mount and 14-feet levelling staff, cost about
£28. Because an accuracy of better than three inches in
1,000 ft. is required, it may be necessary to check and
calibrate the instrument against a really good level.
(e) The proformae. These were prepared from a list of species
made by the author during a brief visit to Wrabness a few
weeks earlier. A similar list could have been compiled without
visiting the site; this would have been of more general
application but unnecessarily long. Copies were printed side
by side on to sheets of foolscap duplicating paper which were
cut in two before use in the field. The proforma is illustrated
in Fig. 1.
(d) Measuring tapes. Several 100-feet plastic-coated, linen tapes.
(f) Bamboo canes. These were conveniently 3-feet long.
(g) A supply of small, tie-on labels, polythene bags and elastic
bands.
Figure 1 The proforma