Instructions for the Galilee Work 123 



distance circle east, face of needle No. 3 east, microscopes direct (D) and reversed {R); long 

 distance, circle east, face of needle No. 3 east, microscopes D and R. Next long distance, circle 

 west, face of needle No. 3 west, microscopes D and R, and finally short distance, circle west, 

 face of needle No. 3 west, microscopes D and R. Note that needle No. 3 is not turned around 

 (mverted) throughout swing; if necessary, the number of readings on each end of the needle, 

 for deflection, may be reduced to a single good one, although, if possible, it will be better to get 2 

 readings. 



(To vary this program somewhat, for the swing at the next station, deflections might be 

 made on first helm and loaded dip on return swing, making the deflections this time throughout 

 with face of needle No. 3 turned away from observer, and the loaded dip with needle No. 4 

 throughout swing Ukewise turned away from observer. This method of observing might, 

 advantageously, alternate with the preceding one. The point is that for any one swing circle 

 east and west should be taken on each heading, but the suspended needle, after being carefully 

 cleaned and mounted, should not be touched again throughout the swing.) 



d. It will be highly desirable to obtain between the prescribed principal swings occasional 

 swings, securing inclination and intensity observations as follows: On first-helm swing, regular 

 dip observations with the better of the two needles selected, e. g., No. 2, not reversing polarity, 

 however, during the swing, but remagnetizing needle before swing. If for one station, A end 

 of needle is down, then for the next station have B end down, etc. On other-helm swing, make 

 intensity observations, either with loaded dip alone or with deflections alone (using one or two 

 distances, as circumstances permit). If at first station, loaded-dip intensity observations were 

 made, then at the next station deflections might be secured. Whether the regular-dip observa- 

 tions precede or follow the intensity observations is immaterial, though it would be better to 

 alternate the sequence and thus vary the accidental conditions. Again, as before, the sus- 

 pended needle will not be turned around (inverted); for one station it might be towards 

 observer, and for the next station away from observer. However, circle E and W should 

 always be taken if conditions permit. If, on these intermediate swings, dechnations can be 

 obtained with either one of the Hquid compasses (Ritchie or Negus), the opportunity should be 

 embraced. 



5. Swings in harbors. — When conditions permit, the more elaborate program which involves 

 turning around (inverting) of suspended needle of sea dip-circle, on each heading, as per directions 

 for swing, Nos. 2 and 3 at San Diego, January 31 and February 8, 1906 (pp. 120-122), should be 

 followed as well as possible. Otherwise the method will be the same as given in 4 a, 4 b, and 4 c above. 

 There will be no objection against securing two series of swings, once upon entry into port and next 

 upon departure. The necessity of this will depend upon length of stay and possible changes made, 

 and must be left to the commander's judgment; what is aimed at is sufficiently clear from these 

 directions and those for the San Diego swings. 



6. Magnetic observations on ship's course. — The attempt should be made to secure some magnetic 

 observations daily, according to extent possible. On days of swings, the following observations are 

 not obligatory. It may happen, however, that, because of cloudiness, every opportunity will have 

 to be seized for declination work. For the observations between swings, the general program will be: 



Simultaneous observations of inclination and intensity with sea dip-circle 35, and horizontal 

 intensity with sea deflector. The work with the sea dip-circle will embrace all positions, as in 

 land work, and will be arranged thus : Regular dip with two needles. No. 2 and another selected 

 one with polarity of both needles A or B, as case may be ;' next loaded dip, then deflections with 

 both distances followed by another set of loaded dip, and finally regular dip with both needles, 

 polarities reversed. The work with sea deflector 1 wiO include observations with both magnets 

 (No. 45 and NL), short distance, letters "up' ' and "down," hence, a minimum of 4 sets. The 

 endeavor should be to secure 2 sets for each combination, as on the previous cruise. Also 

 declinations are to be made with the Ritchie standard compass (RIB) in accordance with the 

 above remarks. 



7. Occasional Magnetic Observations. — 



a. It will be highly desirable to secure, whenever feasible, simultaneous observations for 

 declination with both the Ritchie standard (RIB) and the Negus hquid compass (Dl). The 

 work thus far arranged provides for independent determination of each element, except dechna- 

 tion ; hence the desirability of using, whenever possible, both compasses for the declination work 

 on days between swings. 



'To help guard against error, both needles, before beginning observations, should be remagnetized the same way each 

 time, 80 that for both the A end or the B end will be down. 



