ON MAGNETICAL AND METEOROLOGICAL OBSERVATIONS. 149 



Munich with London by a similar chain of observations of the magnetic 

 constants at Stuttgard, Tubingen, Heidelberg, Manheim, Mayence, Cologne, 

 Aix la Chapelle, Brussels and other places. 



Itinerant Observations not in the nature of Formal Survei/s, Naval Observa- 

 tories, and other Local Determinations. 



Portable magnetometers, accompanied with Lieutenant Riddell's instruc- 

 tions for their use, have been sent not only to the fixed observatories, but also 

 to Sir E. Belcher in China, Captain Blackwood in Torres Straits, Captain 

 Graves at Malta, Captain Barnett at Bermuda, Captain Otter on the north 

 coast of Scotland, and Captain Bayfield in the St. Lawrence. Two sets have 

 also been ordered for the American Coast Survey, the one to be used by Prof. 

 Bache, the other by Prof. Renwick. The officers of the Royal Artillery at 

 Newfoundland are also similarly provided. In all these cases, the instruments, 

 previous to their despatch, have been carefully examined at Woolwich, and in 

 several instances the constants of temperature, &c. determined for each mag- 

 net, and a proper supply of blank forms for the entry and work of the obser- 

 vations adjoined. And we have reason to expect that term observations and 

 absolute determinations will be received from all the quarters above enu- 

 merated. Valuable contributions of this nature from Captains Blackwood, 

 Belcher and Otter have already come to hand. 



Publications relating to Terrestrial Magnetism. 



Among the more generally useful and practically important publications 

 relating to this science, must be considered the elaborate and admirably ar- 

 ranged and digested work of Lieutenant Riddell above alluded to, entitled 

 " Magnetical Instructions for the use of Portable Instruments adapted for 

 Magnetic Surveys and Portable Observatories." Full and complete instruc- 

 tions of this nature, adapted to the species of instruments now become of 

 universal or nearly universal employment, whether intended for differential 

 observations or absolute determinations at fixed stations, or for magnetic sur- 

 veys and other local operations, had long been greatly wanted ; and in fact 

 great inconvenience had been experienced, on all hands, owing to the want 

 of an authentic digest of the kind adapted to the present advanced state of 

 the subject. It was reasonable to expect that, in a subject so new as mag- 

 netism, some of the instruments and methods by which the investigation was 

 in the first instance proposed to be carried on, should have proved inadequate 

 to their purposes. Such has been found to be the case, particularly in refer- 

 ence to that highly important branch of the inquiry, the secular changes. 

 The indisputable evidence of inadequacy, the contrivance of instruments or 

 methods to be substituted, the execution of those instruments, their trial and 

 proof, and their subsequent transmission to the stations with full directions 

 for their use, is all a work of time, and pro tanto has tended to diminish the 

 period for which the observatories can be considered to have been thoroughly 

 effective for their proposed objects ; all this has proved an anxious as well as 

 very laborious part of the occupation of the Ordnance establishment, of which 

 the strength was calculated solely for the duties of reduction and publica- 

 tion. There being no head-quarter observatory, where such questions would 

 be examined and deficiencies supplied, a large portion of the attention of that 

 establishment has been necessarily occupied in this work. The work in ques- 

 tion will show the labour that this has occasioned ; it occupied indeed, almost 

 exclusively, for more than a twelvemonth, the thoughts and time of Lieutenant 

 Riddell, Assistant Superintendent, whose previous employment as director of 



