Descriptions of Instruments 5 



"While the figures given in the above summary show that, thanks to the means 

 provided by the Trustees of the Carnegie Institution of Washington, and the zeal 

 of the observers, a large amount of work has been accomplished of interest not 

 alone to the investigator of the Earth's magnetism but to the geographer and to the 

 geologist as well, the record we may be proudest of is the fact that the entire work 

 described was accomplished without loss of life. It is not possible to individualize 

 here the remarkable work accomplished by the various observers. Suffice it to say 

 that many of the expeditions, frequently embracing comparatively unexplored 

 regions, have been attended with more or less danger, and have presented special 

 difficulties which had to be surmounted. They represent geographic achievements 

 as well as scientific work successfully accomplished under trying conditions. Thus, 

 for example, in the present volume will be found the results obtained on such special 

 expeditions as the difficult coastal trip in Western Africa, the crossing of the Sahara 

 from Algiers to Timbuktu and thence to Lagos, Nigeria; the complete crossing of 

 Australia from south to north, and of South America from east to west and north 

 to south; extensive canoe expeditions in British North America to Hudson Bay, etc. 



The general methods followed, both in the observational work and in the com- 

 putational, as described in Volume I, have continued the same. The instrumental 

 equipments have also been, in general, the same as before, with the exceptions 

 which will be found noted in the proper place. Likewise the results have been 

 tabulated in accordance with the decisions previously reached. The interested 

 reader must be referred to Volume I for any desired information under these heads, 

 as also for specimens of observations and of computations and descriptions of some 

 of the instruments, with accompanying illustrations. 



DESCRIPTIONS OF INSTRUMENTS.^ 



MAGNETOMETERS. 



Since the publication of Volume I, the Department of Terrestrial Magnetism 

 has designed and constructed two new styles of the universal type of magnetometer. 

 The designations of these, as well as those described in the previous volume (pp. 2-1 L) 

 are as follows: 



1. The so-called theodolite-magnetometer type in three designs, viz : (a) and (6) of the Depart- 

 ment of Terrestrial Magnetism, similar, respectively, to magnetometers Nos. 3 and 13, and (c) of 

 the United States Coast and Geodetic Survey, similar to No. 20. 



2. The Kew type of magnetometer in two designs, with auxiliary theodolites for astronomical 

 work, viz: (a) the regular design as constructed by Elliott Brothers, similar to No. 73, and (6) the 

 Magnetic Survey of India design, similar to No. 36. 



3. The light and portable type used in the Magnetic Survey of France, similar to No. 11. 



4. The universal magnetometer type in three designs, viz : (a) the design of Eschenhagen and 

 constructed with modifications by Tesdorpf, similar to No. 2025; (h) the design of the Department 

 of Terrestrial Magnetism, similar to Nos. 14, 19, 20, 21, and 22; (c) the design of the same Depart- 

 ment, similar to Nos. 23, 24, 25, 26, and 27. 



'For Progress Report on "Improvement of Appliances for Measurement of the Earth's Magnetic Elements by Magnetic 

 and Electric Methods," see L. A. Bauer's article in Terr. Mag., vol. 19, pp. 1-18. 



