230 



Report on Terrestrial Morg?ietism. 



[JULY 



ing in their nature and most obscure in their laws, in a manner that 

 shrill 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 If. de Humboldt should be most cordially received by the 

 Royal Society. This society is here called upon, as a member of a 

 great confederation, to co-operate with several other members, already 

 in active co-operation, for the attainment of an object which ought to 

 be common to all : and to such a call the Royal Society can never be 

 deaf. Those who know best what has been done by co-operation on a 

 well-digested system, and what remains undone in many departments 

 of science for the want of it, can best appreciate the benefits that would 

 accrue to science by the adoption of the extensive plan of co-operation 

 advocated by If. de Humboldt. Independently of our acquiring a 

 knowledge of the laws which govern the phenomena here proposed to 

 be observed, we ought to look to the eflec t which the adoption of such 

 a plan may have on other branches of science. The example being 

 thus once set of extensive co-operation in a single department of science, 

 we may anticipate that it would be eagerly adopted in others, where, 

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

 it is regarding the phenomena of terrestrial magnetism, still much re- 

 mains to be accomplished, which can scarcely be effected by any other 

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

 fic societies in Europe directed to the prosecution of inquiry, in each 

 department of science, according to the plan of co-operation best adapt- 

 ed 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 connect- 

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

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

 referred, is this : — However defective ordinary dipping instruments 

 may be considered to be, there are few persons who have had oppor- 

 tunities either of making observations with the ordinary instruments 

 for determining the variation of the needle, or of comparing those made 

 by others by the usual methods with such instruments, who will not 

 admit that these instruments and methods are fully as defective — pos- 

 sibly much more so. Thus, however we may multiply the points on 

 the earth's surface at which such observations 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 discordances which may be found are due to 

 errors of observation, or are indicative of the fallacy of these laws. 

 Ills source of uncertaiir.v most, in a great measure, if not wholly, be 



