16 Ocean Magnetic Observations, 1905-16 



ments could readily be communicated. Usually, in past expeditions, the reduction of obser- 

 vations has been deferred until the close of the work, when possible improvement, suggested 

 by the results, could no longer be made. Moreover, the publication of results generally 

 occurred so long after the observational work was completed that other expeditions were 

 unable to profit by the experience gained on previous ones. There appears to be nothing so 

 harmful to research as lack of promptness in the reduction of observational data and in the 

 publication of results. Not infrequently delay in making the data available has caused the 

 defeat of the very purpose for which the observations were undertaken. 



To accomplish prompt reduction, the following principles were followed as closely as 

 possible : 



First, to have instruments, methods of observation, and methods of computation 

 all form one harmonious whole, not to be treated as though they were independent of one 

 another. With instruments properly constructed and carefully tested, it has been found 

 possible to get absolute values of the magnetic elements with an accuracy sufficing for all 

 purposes — scientific as well as practical. 



Second, to adopt such observing program as would fit the purpose, the instruments, 

 and the form of computation. A good scheme of observation takes advantage of the capa- 

 bilities of an instrument in the briefest possible time and is so arranged that independent 

 computers can get but one result, if no computation errors have been made. Observers 

 have had impressed upon them the fact that their observations have no value until com- 

 puted and, hence, that they must bear the computer in mind and consider what his task 

 will be. 



It was thus possible for the Director to be almost as closely in touch with the work as 

 though he himself were continuously on the vessel. 



One of the first lessons learned was that it is rarely, if ever, possible to have ideal con- 

 ditions in ocean work. In consequence, the development of good judgment in the observer 

 has been one of the prime requisites. Sometimes in an instant he has to be able to change 

 his plan of observation and be content with a fair degree of accuracy, or get no observations 

 at all. 



REGARDING OBSERVATION FORMS. 



As it is difficult, even for a magnetician experienced in observatory work or in mag- 

 netic surveys on land, to form an adequate conception of the problems confronting one in 

 ocean work, there will be given later in more detail the directions followed in the observa- 

 tional work, as well as specimens of observations and of computations. Various practical 

 schemes for making satisfactory ocean observations had to be devised, and a large number 

 of printed forms were prepared for simplifying both the recording and the computing of 

 the various kinds of observations. Comparatively few hints could be gleaned from the 

 pubfished reports of previous expeditions as to the best and most efficacious methods of 

 determining ship deviations for all three magnetic elements. While considerable work had 

 been done with regard to observations for declination deviations, comparatively Uttle was 

 available for guidance in obtaining correctly and accurately the dip and intensity devia- 

 tions. Fortunately this troublesome part of ocean magnetic work has been eliminated on 

 the Carnegie. 



Suitable printed forms are a very great help not only in properly recording observa- 

 tions, but also in quickly calling attention to the omission of important information required 

 by an office computer who, necessarily, is unacquainted with the circumstances under which 

 the observations were made. A proper and suitably arranged record of observations reduces 

 the labor of computation. 



