The method to be employed in ascertaining the exact position of
the float from time to time is a matter which requires careful
consideration, and is dependent upon the degree of accuracy
required according to the importance of the scheme and the
situation of neighbouring towns, frequented shores, oyster
beds, and other circumstances likely to be injuriously affected
by any possible or probable pollution by sewage.

One method is to follow the float in a small boat carrying a
marine compass which has the card balanced to remain in a
horizontal position, irrespective of the tipping and rolling of
the boat, and to observe simultaneously the bearing of two
prominent landmarks, the position of which on the plan is
known, at each of the quarter-hour periods at which the
observations are to be taken. This method only gives very
approximate results, and after checking the value of the
observations made by its use, with contemporary observations
taken by means of theodolites on the shore, the writer
abandoned the system in favour of the theodolite method, which,
however, requires a larger staff, and is therefore more
expensive. In every case it is necessary to employ a boat to
follow the float, not only so as to recover it at the end of
each day's work, but principally to assist in approximately
locating the float, which can then be found more readily when
searching through the telescope of the theodolite. The boat
should be kept about 10 ft to 20 ft from the float on the side
further removed from the observers, except when surface floats
are being used to ascertain the effect of the wind, when the
boat should be kept to leeward of the float. Although obviously