234 



Report on Terrestrial Magnetism. 



[July* 



should be established in the north of Scotland and in the west of Ire- 

 land. 



M. de Humboldt adverts to another very interesting class of magne- 

 tical observations, those in the mines of Freyberg. The mines of Corn- 

 wall from their great depth, some being 1200 feet below the level of the 

 sea, are peculiarly well adapted for observations of this description ; 

 and, from the spirit with which philosophical 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 appear best 

 adapted to furnish valuable results, and having likewise pointed out 

 the facilities which some afford for the execution of this plan of ob- 

 servation, immediately that the nature of the instruments to be em- 

 ployed has been determined upon, and that such instruments can be 

 provided, it may be proper to advert 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 observa- 

 tory 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 advance scientific knowledge. Thus, 

 altogether, there might be formed a most extensive spread of stations, 

 in which the principal expense would consist in the purchase of the 

 requisite instruments ; and the means of establishing stations where 

 the same facilities do not exist might afterwards be taken into consi- 

 deration. As it would be necessary that, at all the stations, observa- 

 tions 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 Humboldt's communication on 

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

 best calculated to attain the objects in view by the establishment 

 of magnetical observatories. This is a subject on which it will be 

 most proper to enter fully when their establishment has been deter- 

 mined upon ; and we would recommend that then the Committee should 

 be appointed to investigate the subject, and that this Committee should 

 report to the Council of the Royal Society what instruments they con- 

 sider it would be most advisable to adopt at all the stations, and, at the 

 same time, give in an estimate of the expense that must be incurred for 



