CHAP. XXL] OBTAINING ANGLES AT THE BEACONS 485 



out incurring the risk of being unable to obtain a satisfactory 

 fix at this terminal position (see Fig. III.). 

 A suitable arrangement would be for — 



X to drop Beacons Nos. 4, 7, 10, and 13, 

 Y ,, „ ,, 5, 8, and 11, 



Z „ „ „ 6, 9, 12, and 14, 



following in approximately numerical sequence. 



The rough plot is kept up to date as we proceed by compass 

 bearing and angle, and all available data recorded as each 

 beacon is dropped. 



SECTION VI. 

 OBTAINING ANGLES AT THE BEACONS. 



On the necessary beacons being laid out, the work should 

 be so arranged that it is now possible to revisit every beacon 

 in quick succession whilst the tidal stream is running in one 

 direction only, leaving a sufficient subsequent margin of time 

 to enable the several shij)s to take up theii* assigned posi- 

 tions with certainty whilst dayhght remains, should it be con- 

 templated and the weather favourable for connecting the 

 triangulation with the shore objects by night. 



Slack water occurring about midday Avould be very suitable 

 for the present work, which sliould not have up to now occupied 

 more than four hours since commencing. 



X would visit Beacons 13, 8, 5, 3, and 1 in that order. 

 Y „ „ „ 11, 10, 7, 4, 2, in that order. 



Z ,, „ „ 14, 12, 9, and 6 in that order. 



In obtaining these angles some care and forethought is 

 necessary, involving a systematic procedure if we desii'e to 

 obtain accurate results. 



Some such method as the following should be adopted. 



Before coming up to the Beacon. — 1. Ship to be stemming 

 the tidal stream at slow speed with the beacon about one cable 

 distant, and the ship heading in the same direction as she will 

 be when subsequently stopped at the beacon. 



2. The assistants in readiness to observe the angles for which 

 they are detailed, the approximate data being taken from 



