Mounting of Instruments on the Galilee 



27 



Scale in Feet 

 m I I M I I I I I I I I I I I I 

 10 4 8 12 16 



Scale 

 |""i'i"| 



in Meters 



gimbals and adjustable weight (see p. 21). The base of this stand is flat and rectan- 

 gular; it was fastened to the deck by four f-inch brass bolts, one in each corner of the base. 

 Under each corner of the base were soft-rubber cushions, through which the bolts passed ; 

 these cushions were between 3 and 4 inches square and about Ij inches thick and the nuts 

 on the under ends of the bolts were set up firmly. A small pocket-compass, used in the initial 

 work for approximate orientation purposes, was placed during observations on top of the 

 flat base of the stand inmiediately in front of the upright standard; it was thus nearly 4 

 feet from the center of suspension of the dip needles; hence, there was no danger of its 

 having a disturbing effect on them. 



Standard Ritchie liquid compass 29971 {RlA), used for determining the magnetic dec- 

 lination, was mounted on a Ritchie U. S. Navy standard binnacle, made of gun metal, cast 

 in one piece, and devoid of all compensating devices. 

 As seen in Figure 1, A, RlA was centered on the bridge 

 8 feet 4 inches forward of the center of D.C. 169. 



Negus liquid compass 31974 with sea deflector 1 (Dl), 

 used primarily for determining the horizontal intensity, 

 but also for secondary observations of the magnetic 

 dechnation, was mounted on a Negus hollow, cylindrical, 

 wooden binnacle, devoid of all compensating devices. 

 It was centered on the bridge 8 feet 4 inches forward of 

 RlA, and 16 feet 8 inches forward of D.C. 169. 



Kelvin dry compass {K) , used for experimental obser- 

 vations of magnetic declination, and later to test method 

 of determining horizontal intensity at sea by vibration 

 observations, was mounted on a hollow, cylindrical, 

 wooden binnacle, devoid of all compensating devices, 

 of the tyi^e made and sold by T. S. and J. D. Negus. 

 As shown in Figure 1, ^, the center of K was 8 feet 4 

 inches from Dl, 16 feet 8 inches from RlA, and 25 feet 

 from D.C. 169. 



The 4 instruments were carefully adjusted and 

 alined so that their lubber-lines were in the same fore- 

 and-aft plane. Tliis was also invariably done for the 

 rearrangements mentioned below. 



Figure 1 , Plan B, shows the arrangement and spac- 

 ing of the instruments on the observing-bridge for the 

 balance of Cruise I, San Diego to Fanning Island and 

 return, August 24 to December 20, 1905. In order to increase somewhat the distances 

 between the 3 chief instruments, D.C. 169, RlA, and Dl, the KeMn compass (K) was 

 temporarily removed and used as the ship's steering-compass, to replace the inadequate 

 one supphed with the vessel by the owners. It was thus possible to increase the distance 

 between the centers of any two adjacent instruments to 10 feet 10 inches. 



© 



K 



© 

 Dl 



© 

 RIB 



© 

 35 



Aft 



Fia. 1. 



-Plans of the Observing-bridge on 

 the Galilee. 



Cruises II and III, 1906 to 1908. 



Shore experiments at San Diego in August 1905 had shown that the original distance 

 apart of 8 feet 4 inches, was sufficient to provide against any mutual disturbing effect 

 of the instruments on each other in ordinary work. However, to be fully safeguarded, and 

 in order to make readily possible experiments with any one of the instruments while 

 observations were under way with the others, the increased distance apart of 10 feet 10 

 inches was adhered to throughout Cruises II and III. In order to admit of restoring the 

 Kelvin compass (K) on the bridge, the latter was lengthened so as to reach within about 



