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shall not only give greater precision to the observations, but at the 

 same time render all the results strictly comparative. 



There are, however, other grounds on which such a proposition as 

 that made by M. de Humboldt should be most cordially received 

 by the Royal Society. This Society is here called upon, as a mem- 

 ber of a great confederation, to cooperate with several other mem- 

 bers, already in active cooperation, for the attainment of an object 

 which ought to be common to all; and to such a call the Royal So- 

 ciety can never be deaf. Those who know best what has been done 

 by cooperation on a well-digested system, and what remains undone 

 in many departments of science for the want of it, can best appre- 

 ciate the benefits that w r ould accrue to science, by the adoption of 

 the extensive plan of cooperation advocated by M. de Humboldt. 

 Independently of our acquiring a knowledge of the laws which go- 

 vern the phenomena here proposed to be observed, we ought to 

 look to the effect which the adoption of such a plan may have on 

 other branches of science. The example being thus once set of 

 extensive cooperation in a single department of science, we may 

 anticipate that it would be eagerly adopted in others, where, al- 

 though our knowledge may be in a much more advanced state than 

 it is regarding the phenomena of terrestrial magnetism, still much 

 remains to be accomplished, which can scarcely be effected by any 

 other means. We might thus hope to see the united efforts of all 

 the scientific societies in Europe directed to the prosecution of in- 

 quiry, in each department of science, according to the plan of co- 

 operation best adapted for its development. 



We must now, after these remarks on the general bearing of M. de 

 Humboldt's communication, go somewhat into detail on points con- 

 nected with it. One point of view in which we consider the proposed 

 plan of great importance, and to which M.de Humboldt has not ex- 

 pressly referred, is this. However defective ordinary dipping instru- 

 ments may be considered to be, there are few persons who have 

 had opportunities either of making observations with the ordinary 

 instruments for determining the variation of the needle, or of com- 

 paring those made by others by the usual methods with such in- 

 struments, who will not admit that these instruments and methods 

 are fully as defective — possibly much more so. Thus, however we 

 may multiply the points on the earth's surface at which such obser- 

 vations .may be made, still great uncertainty must always rest upon 

 such determinations of these two important elements ; and in all 

 comparisons of such observations with laws, whether empirical or 

 deduced from theory, it will ever be doubtful whether the discord- 

 ances which may be found are due to errors of observation, or 

 are indicative of the fallacy of these laws. This source of uncer- 

 tainty must, in a great measure, if not wholly, be obviated by obser- 

 vations made at fixed stations, with instruments of similar construc- 

 tion, which have been carefully compared with each other. And 

 we have no hesitation in stating our opinion that more would be 

 done in determining the positions of the poles of convergence and 

 of verticity on the earth's surface and other points, most important 



