88 SCIENCE PROGRESS. 



corrected by permanent magnets, by horizontal soft iron, 

 and by vertical soft iron, an accurate knowledge of the 

 magnetic elements Dip and Intensity obtained from obser- 

 vations on land and at sea was essential. 



Before dismissing the subject of the above application 

 of magnetic observations, it may be remarked that we have 

 now heavily armed, protected steel cruisers steaming over all 

 parts of the world with less change of deviation of the 

 compass than the wood-built Erebus and Terror of Ross's 

 Antarctic expedition, and this remarkable result could not 

 have been achieved if the terrestrial magnetic observer had 

 not done his work. 



Moreover, if magnetic observations are not continued 

 the secular change of the magnetic elements will soon 

 commence to mar the precision with which our rapidly 

 moving ships traverse the globe. 



The voyage of the Challenger in 1872-76 contributed 

 the most valuable series of observations of the magnetic 

 elements in modern times, when the large areas of the 

 principal oceans traversed by that vessel during three and 

 a half years are taken into consideration. These observa- 

 tions, combined with those taken from every available 

 source, both British and foreign, between the years 1865-87, 

 formed the materials from which the magnetic charts of 

 1880 were compiled (see vol. ii., Physics and Chemistry, 

 part vi., Voyage of H.MS. "Challenger"). 



The Challenger only crossed the Antarctic circle at one 

 point in longitude 78° E M and, therefore, although we know 

 large secular changes to be going on south of 40 S. we have 

 no measure of the amount, nor anything like an accurate 

 knowledge of distribution of the earth's magnetism in those 

 regions. This points to the necessity for a new Antarctic 

 expedition. 



In the year 1888 the late Professor J. C. Adams was 

 provided with a complete set of magnetic charts for the two 

 epochs 1842-5 and 1880 previously mentioned, and as it 

 was known he had directed his profound mathematical 

 ability to the analysis of the results contained in them, it 

 was hoped that some new and important light might be 



