EXTRACTS FROM DIRECTOR'S INSTRUCTIONS FOR CRUISES AND 

 OBSERVATIONAL WORK ON THE CARNEGIE. 



The following extracts from the Dkector's instructions to those in command of the 

 Carnegie, from time to time, will serve to explain the routes prescribed for the vessel and 

 the methods of observation adopted for the various kinds of work. They will aid in 

 showing how the observations were made at successive stages of the work, and how the 

 methods and instrumental appliances were developed and modified as experience suggested. 

 It will be noticed that, although the Carnegie is a strictly non-magnetic vessel, nevertheless 

 the instructions called for occasional swings of the vessel in order to make desired tests, 

 both as to the absence of ship deviations and of "instrumental deviations" (see p. 18). 

 From the discussion on page 436 it will be seen that the observations made on these swings 

 served a useful purpose, and gave the means of judging as to the accuracy of determination 

 of magnetic elements aboard the Carnegie under harbor conditions. 



CRUISE I OF THE CARNEGIE. 1909-1910. 

 From Route Instructions of July 14, 1909, to W. J. Peters at Brooklyn. 



1. Leaving Brooklyn as soon as feasible, and after the trial observations and swings at Gardiners 

 Bay have been completed, a course will be shaped for St. John's, Newfoundland, crossing the 60th 

 meridian in about latitude 41° to 42°. 



2. St. John's, N. F. — The C. I. W. (Carnegie Institution of Washington) magnetic station of 

 1905 is to be reoccupied and such additional shore observations are to be made as may be found 

 necessary. * * * 



3. After the completion of the work at St. John's, the vessel will follow a course to Falmouth, 

 England, as nearly direct as possible, crossing the thirtieth meridian in about latitude 51°. Such 

 shore observations as may be required will be made, and the vessel will be swung in Falmouth 

 Harbor. 



4. Leaving Falmouth early in November, the sailing route will be followed to Madeira, and, 

 after making there the requisite shore observations, proceed next to New York via Bermuda, inter- 

 secting the fortieth meridian in about latitude 22° north. * * * 



5. Bermudas. — These islands are greatly disturbed magnetically and every care must be taken in 

 the proper selection of stations for shore work. 



6. New York. — Return should be made not later than about February 1, 1910. After the 

 completion of whatever work may be necessary, the vessel will be turned over to the Tebo Yacht 

 Basin Company for the copper sheathing of the bottom. * * * 



From Instructions fob Scientific Work on Cruise I. 



1. Observe the three magnetic elements daily unless conditions prevent. 



2. Declination. — Corresponding observations with the two compasses (CI and D3) are to be 

 made, whenever possible, and the causes of differences investigated. 



3. Observations with sea dip-circle. — Loaded dip will be required only every third day, and in 

 between the total-intensity work will be confined to deflection observations. In deflection work, 

 for short distance, read extremes of arc; for long distance, set microscope-thread on middle of arc 

 by method of repeated bisection. When combining dips, give results from regular dip needles 9 

 and 10 each double weight, and deflected dips, each distance, single weight, or what amounts to the 

 same thing, treat the mean result from short and long distances as equivalent to a result with needle 

 9 or 10. The possibility of level error in dip obser\'ations requires attention. In addition to setting 

 the foot-screws according to the foot-screw readings, the matter of whole turns should be controlled 

 also for every mounting of the instrument. To facilitate this, brass gages should be made, or some 

 other device be used. It is essential that the level position of the dip circle be controlled each time, 

 and an entry be made on the dip sheets that this was done before the observations were made. 



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