Observations at Lightships 
114. Through the cooperation of the Coast Guard arrangements are made from 
time to time for current observations to be taken by the officers and crews of lightships 
while on their regular stations. These observations are taken hourly with a 15-foot 
current pole and log line, using a stop watch for timing the run-out of the pole and a 
pelorus for determining the direction of the current. 
115. Pelorus.—The pelorus is described in paragraphs 41-42. The instrument is 
to be mounted in the stern of the vessel with the 0° mark forward or inboard and with 
the line through this mark and the center of the instrument either exactly in the fore- 
and-aft line of the vessel or exactly parallel to it. 
116. Current pole and log line.—Descriptions of these instruments will be found 
in paragraphs 25-30. The log line should be marked for an observational interval of 
60 seconds, the distance between the marks for the whole knots being 101 feet 4 inches 
and the distance between the marks for the tenths of a knot, 10 feet 1.6 inches. There 
should be not less than 80 feet of stray line. The log line must be checked occasionally, 
the measurement being made when the line is wet, and any error in the distance be- 
tween marks noted in the record book. If the line has been broken, it must be carefully 
re-marked after repairs and a note to that effect entered in the record book. <A spare 
pole and line should be kept aboard the lightship at all times so that an occasional loss 
of these items will not interrupt the current record. 
117. Record book.—Form 270a, Hourly Current Observations, has been especially 
designed for recording the hourly current observations taken on lightships. Each 
record book is to contain the observations for a single calendar month. The name of 
the station with the names of the master and observers and the period of time covered 
by the record should be written on the front cover. After the completion of the record 
for any month, the book is to be mailed at the first opportunity to the Director, Coast 
and Geodetic Survey, Washington, D. C. Official envelopes with printed address will 
be provided for the purpose. A copy of the deviation card for the ship’s compass should 
be forwarded with the first record book for the station and with the record book follow- 
ing a change of lightships at the station or a compass adjustment. All current-observ- 
ing equipment, including record books and instructions, should be transferred to the 
relieving lightship when there is a change of lightships at a station. 
118. Time used.—Correct time is of great importance and each record book must 
have a statement on the first page telling the kind of time used and whether Standard 
or Daylight Saving time is followed. The clock or watch used for the observations 
should be checked frequently by radio time signals. 
119. Observing velocity.—Have everything in readiness a little before the hour, and 
exactly on the hour start paying out the stray line. When the initial mark of the 
graduated portion of the log line passes some fixed reference point (a mark on the 
taffrail is convenient), press the stem of the stop watch. Continue to pay out the 
line for exactly 1 minute, taking care not to pay it out faster than the pole can carry 
it away; then check the line and read the velocity of the current to the nearest tenth 
of a knot as indicated by the mark on the line nearest to the fixed reference point. 
The number of knots and tenths must be immediately recorded in their respective 
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