Report on Terrestrial Magnetism. 



M. de Humboldt adverts to another very interesting class of 

 magnetical observations, those in the mines of Freyberg. The 

 mines of Cornwall from their great depth, some being 1200 feet 

 below the level of the sea, are peculiarly well adapted for obser- 

 vations of this description; and, from the spirit with which phi- 

 losophical inquiry has been carried on in that part of England, 

 we do not anticipate that much difficulty would occur in the 

 establishment of a magnetical station in one of these mines. 



Having enumerated the stations which by their position ap- 

 pear best adapted to furnish valuable results, and having like- 

 wise pointed out the facilities which some afford for the execu- 

 tion of this plan of observation, immediately that the nature of 

 the instruments to be employed has been determined upon, and 

 that such instruments can be provided, it may be proper to ad- 

 vert to stations where, although the same facilities do not exist, 

 we consider that zealous and able observers might be obtained 

 without much difficulty. We conceive that such is the case in 

 Newfoundland, in Canada, at Halifax, Gibraltar, in the Ionian 

 Islands, at St Helena, and Ceylon ; and we have authority for 

 stating that there would be no difficulty in obtaining observers, 

 in the Mauritius, and even at the Colony on the Swan River, 

 the latter being a most desirable station. We have not alluded 

 to the observatory at the Cape of Good Hope ; if, however, no 

 such establishment existed, the presence of Sir John Herschel 

 would ensure co-operation there, in any plan calculated to ad- 

 vance scientific knowledge. Thus, altogether, there might be 

 formed a most extensive spread of stations, in which the princi- 

 pal expense would consist in the purchase of the requisite instru- 

 ments ; and the means of establishing stations where the same 

 facilities do not exist might afterwards be taken into considera- 

 tion. As it would be necessary that, at all the stations, ob- 

 servations of the barometer, thermometer, and of atmospheric 

 phenomena, should be made simultaneously with the magnetical 

 observations, these would altogether form a mass of valuable 

 meteorological information which it would be scarcely possible 

 to collect by any other means. 



There is one point in M. de Humboldfs communication on 

 which we have not yet touched : the nature of the instruments 

 best calculated to attain the objects in view bv the establishment 



