Extracts from Instructions, 1909-16 319 



D. C. 189 appears to be an exceptionally good instrument and should therefore have every care 

 bestowed upon it to guard against accident. No. 203 is only to be used in case of emergency, but 

 observations will be made with it regularly on land. 



C. Shore Magnetic Observations. 

 1. Until otherwise advised, the same directions apply in general as heretofore, subject to such 

 modifications as the Commander finds necessary according to circumstances. It will be desirable 

 in the determination of the constants for the ship instruments to make the observations either 

 simultaneously with the land instrimaents, or at such time of day when the diunial-variation cor- 

 rections are small, or variable in sign. Descriptions of certain stations to be occupied are furnished, 

 but the Commander is at Hberty to add additional ones as he may find necessary and possible. 



D. Coinputations of Magnetic Observations. 



1. Until otherwise instructed, the computations on the present cruise will be made with the same 

 constants throughout as already supplied. In other words, the constants are not to be changed 

 with every new determination; so also in the land observations for determination of new constants, the 

 computations will be made with the old constants and the corrections, instead, determined. These 

 corrections will be distributed along the cruise and will be applied on the abstract of results. There 

 will thus be avoided frequent changes m the computations on the observation sheets. These compu- 

 tations when revised will remain unchanged thereafter unless some error is discovered in computation. 

 This new method applies to all the magnetic elements. The logarithmic work will in general be 

 carried to four places. 



E. Atmospheric-Electric Observations. 



1. Such observations are to be made as time of observer will permit. They will, in general, 

 be of the same character as on the previous cruise, with such modifications and additions as the 

 observer in consultation with the Commander finds desirable. 



F. Atmospheric-Refractio7i Observations. 



1. These observations will be continued and amplified as may be found possible; the precise 

 directions are left to the Commander. 



G. Meteorological Observations. 



1. These observations will be the same as on previous cruise, with such extensions as the Com- 

 mander finds possible. 



H. Astronomical Observations. 



1. Astronomical observations will be made as on previous cruise in duphcate or triplicate, as the 

 Commander directs, and as often as may be necessary for effective control of geographic positions. 



I. Other Observations. 



1. The Commander will be allowed to include such additional scientific work as he finds possible 

 on board the Carnegie. His attention is called to the need of additional observations on ocean 

 currents. 



Instructions of August 26, 1910, for Swing Magnetic Observations Subsequent to those at Gardiners Bay. 



1. It will in general suffice to secure for each element one complete swing with each hehn, 

 provided all necessary precautions are taken beforehand regarding absence of magnetic articles 

 sufficiently close to affect the results, with respect to satisfactory condition of instrument, etc. 

 The swings for the various elements may be arranged by the Commander to suit the conditions; 

 8 equidistant points will be taken. The Commander is also at liberty to repeat any of the observa- 

 tions or swings as he may find necessary, without unduly prolonging stay in port. Places of swing 

 will not be designated, but will be left to the judgment of the Commander with the remark that it 



