GENERAL BEARINGS OF MAGNETIC OBSERVATIONS. 115 



magnetism. This work was long seriously retarded by the various 

 methods adopted at different observatories for recording their results, 

 obliging those who entered upon a comparison of such results to go 

 through a tedious conversion of them into a common method. It may 

 be said that the first large departure from this objectionable practice 

 occurred when the international polar inquiry of 1882-1883 was under- 

 taken by the various expeditions. 



This was an important step in the right direction, but there remains 

 much to be done, as shown by the ten reports of the British Associa- 

 tion Committee on "the best means of comparing and reducing rnagr 

 netic observations." Their last report consists of an able and suggest- 

 ive paper by Dr. Chree, being the analysis of the results of five years' 

 observations on "quiet days 77 at Kew, and is well worthy of attention 

 as indicative of the present state of our knowledge as regards the diur- 

 nal variation of the three magnetic elements. 



Such investigations only encourage one in the hope that the much 

 required observations in southern latitudes may be undertaken. The 

 observatories at the Gape and Melbourne could do invaluable work if 

 it were carried out on the lines of Kew, for example. 



Lastly, what more is there to be said about magnetic observations 

 and their bearings'? We do not know why the earth is a magnet, the 

 cause of the secular change of its magnetism, why it is subject to solar 

 diurnal, lunar diurnal, sidereal diurnal, and the other variations and 

 disturbances, nor the cause of magnetic storms, although Ave can observe 

 connections between them, earth currents, and aurorae. Whether the 

 causes of all these exist below the surface of, or are external to, the 

 earth, or are a combination of the two, has still to be learnt, and it 

 seems hardly too much to hope that the restless needle will sooner or 

 later be the means of opening up sources of knowledge invaluable to 

 cosmical science, as well as to those only concerned with the planet 

 upon which they dwell. 



When the causes of the secular change are understood, there will be 

 no difficulty in providing the navigator with magnetic charts for years 

 in advance, much as the tides can now be tabulated for his use. In 

 the latter case observation has done its work for several frequented 

 ports, in the former case a vast amount remains to be done, and the 

 word that goes forth is still, as Lord Kelvin thrice said on a kindred 

 subject connected with ships 7 magnetism, "Observe." 



