Instructions for the Galilee Work 119 



examination respecting this matter, and arrange to have this boat stowed elsewhere, if deemed 



necessary * * * 



From Route Instructions of January 20, 1906, to W. J. Peters, San Diego, Cal. 



1. The general route to be covered in the forthcoming cruise is as follows: Leaving San Diego 

 as early in February as circumstances will permit, sail on a direct course for Fanning Island, thence 

 to Apia and Pago Pago, Samoan Islands. If, upon the completion of the work at the Samoan sta- 

 tions, it should be found feasible, proceed next to Suva, Fiji Islands, a cable station. From there, 

 or from the Samoan Islands, as the case may be, take a course to Jaluit Island of the Marshall Groupj 

 where a good harbor will be found and supplies are obtainable, this being an important German 

 trading-station. Proceed next by direct course to San Luis d'Apra, Guam, a cable station; leaving 

 there, pass to the westward until the meridian of Yokohama (140° east) is reached, and thence 

 proceed along that meridian to Yokohama or to the Gulf of Tokio, where a suitable place will be 

 selected for the harbor swing. The aim should be to leave here not much later than July 1, in order 

 to be sure of encountering as good weather conditions as possible on the return trip, going by direct 

 course to Kiska Island of the Aleutian Chain, from there to Sitka, unless otherwise instructed, and 

 then back to San Diego, endeavormg to reach this port in October 1906. [Owing to delayed 

 departure from Yokohama, it was necessary on this cruise to omit the trip to Sitka and return 

 instead by great-circle route to San Diego.] 



2. It will be noticed that this cruise embraces a number of good supply stations, and, likewise, 

 stations for controlling well your chronometers, as also affording facilities for excellent harbor swings 

 and comparisons of instruments at three magnetic observatories (Apia, the German Magnetic 

 Observatory, where one of the temporary observers of the Department, Mr. G. Heimbrod, is at 

 present stationed; next, Tokio, and Sitka). * ♦ ♦ 



From Directions of January 30, 1906, for Swings No. 1 at San Diego, to W. J. Peters. 



1. Assure yourself that everything is in place on board ship as nearly as possible as at sea, being 

 particularly careful about removal of all magnetic articles, as far as possible, in the vicinity of the 

 bridge. Before beginning work, rehearse observers in operations assigned. Arrange to complete a 

 swing, both helms, preferably morning or afternoon, or at least on same day. If conditions do not 

 make 16 equidistant points feasible take 8. [8 equidistant headings were finally adopted.] 



2. First swing, being an experimental one, will be confined to declination observations and com- 

 parisons of compasses on each heading, as follows: 



A. One observer using Ritchie standard compass (RIB). Before beginning observations, 

 mount the new cyhndrical reflector in place of the deteriorated one in the azimuth circle, and 

 take care not to disturb verticality of mounting. Obtain, if possible, on each heading 3 readings, 

 using the reflector and prism, Ukewise 3 readings with ahdade, alternating, preferably from one 

 to the other, so as to determine effectively any possible difference between the two azimuth 

 devices. 



B. A second observer using the Negus compass and azimuth circle (Dl), taking readings and 

 following, as far as possible, the methods under A. 



C. Mount on the gimbal stand an instrument for determining the compass deviations at this 

 position, as required by theory. For this purpose the Kelvin dry compass and bowl, using the 

 better one of the two compass cards, may be fastened to the top of the gimbal rings with the 

 lubber-line as nearly as possible in the fore-and-aft line. * * * No azimuth device will be 

 used, but comparisons be made as prescribed in D. 



D. Comparisons between the Ritchie (RIB), the Negus (Dl), and the compass on the 

 gimbal stand to be made as follows, obtaining 3 readings in each instance : 



When the ship's head is on the course, as shown by the Ritchie standard (RIB), the observer 

 using this instrument will call out "On," whereupon the observers at the other compasses will 

 read their respective cards. There will thus be afforded a check between the deviations 

 obtained independently by the Negus and the Ritchie compasses. Owing to the less advan- 

 tageous position of the Negus, it may happen that the solar observations will be cut out by an 

 intervening mast more frequently than with the Ritchie; the attempt should be made, never- 

 theless, to obtain whatever conditions will permit. 



