Specimen Observations on the Galilee 33 



GENERAL PROPERTY AND SUPPLIES. 



Besides the instrumental equipment listed on pages 28-32, the general property and 

 suppUes aboard the Galilee, 1905-1908, were about as follows: 



L Navigation charts, maps, and atlases of various kinds. 



n. Library of books on astronomy, navigation, mathematics, magnetism (general and terres- 

 trial) , general physics, atmospheric electricity, general chemistry, meteorology, geogra- 

 phy, geology, biology, sailing ships (sails and sail-making, etc.), encyclopedias, diction- 

 aries, and general literature. 

 in. Medical books and supplies. 

 IV. Miscellaneous appurtenances. 



SPECIMENS OF OBSERVATIONS AND OF COMPUTATIONS. 



Reference has already been made, page 16, to the various forms devised for recording 

 and computing the observations made aboard the Galilee. The specimens given in this sec- 

 tion will serve to show the utility of these forms, and at the same time help to make clear 

 the methods of observation and of computation. The specimens are confined to ship work. 

 Those illustrating land work will be found in Volume I, pages 30-41. 



MAGNETIC OBSERVATIONS DURING SWING OF VESSEL. 



First are given specimens of magnetic observations obtained during one of the 

 Galilee's last swings at San Francisco, May 25, 1908. The swing was made with the aid of 

 the tug Liberty, which came alongside about 4'' 30°° a. m. and towed the Galilee to the north 

 of Goat Island, in about 10 to 27 feet of water, practically in the same place where the swings 

 were made when the vessel set out on her work in August 1905. The position was verified 

 from time to time by sextant angles to prominent objects. The swing was on 8 equidistant 

 headings, both helms, first port and then starboard, the tug towing ahead with about 60 

 fathoms of line out. Conditions of sea and weather were good throughout. 



A swing (both helms) had been made two days previously (May 23) and another 

 was made on May 28. On May 23 the tug did not come alongside the vessel until 7 a. m., 

 so that by the time the swings were made the trigonometric conditions were not favorable 

 for observations of the magnetic declination. .Also it was discovered that sea dip-circle 

 189 had been out of level during the first half of the swing on that day. Accordingly, a 

 thii'd swing was made on May 28, the tug coming alongside at sunrise. The specimen 

 inclination observations (p. 44) are taken from the swing of May 28, 1908. The swing on 

 May 25 began with port helm, heading west, and was, accordingly, made in the order: 

 W, NW, N, NE, E, SE, S, SW. The vessel was next swung with starboard helm as follows: 

 E, NE, N, NW, W, SW, S, SE. 



Declination Observations, San Francisco Bay, May 25, 1908. 



Page 34 contains the magnetic-decUnation observations (Form 21) made aboard the 

 Galilee in San Francisco Bay on May 25, 1908, a. m., during the first half of the port-helm 

 swing, using the standard Ritchie compass R3C (see p. 31) and employing first the prism 

 method and, next, the alidade method. 



The details are sufficiently clear from the headings and adjacent designations to 

 require no further explanation. It will be seen that on each heading there were 5 settings 

 made on the Sun, using the prism, next 5 settings, using the alidade; the average time for 

 5 settings was about 25 seconds, the 10 settings requiring about 1 minute. Whether 

 the prism or alidade was used first depended somewhat upon the brightness of Sun. 



On page 35 is found a specimen "Computation of Ocean Declination Observations" 

 (Form 22). Before entering on Form 22, the data from Form 21, instrumental corrections, 



