611 



concomitant auroral phenomena, in a locality which is perhaps one of 

 the most important on the globe for such investigations. Their 

 observatory, placed on the sand of the sea-shore, was constructed of 

 slabs of ice, and was lined throughout with seal skins. The instru- 

 ments had been supplied from the Woolwich establishment, with the 

 requisite instructions for their use, and the observations were made 

 and recorded precisely in the same manner as those in the Colonial 

 Magnetic Observatories. The observations were sent by Captain 

 Maguire to the Admiralty, and were in due course transmitted to 

 General Sabine, by whom they were subjected to the same processes 

 of reduction as those in the colonial observatories : the results are 

 given and discussed in this communication. 



A sufficient body of the larger disturbances to permit an exami- 

 nation of their laws having been separated from the rest of the ob- 

 servations, it was found at Point Barrow, as elsewhere wherever a 

 similar investigation has been made, that in regard to the frequency 

 of their occurrence, and to the mean amounts of easterly and west- 

 erly deflection produced by them, the disturbances follow system- 

 atic laws depending on the hours of solar time. The laws of the 

 easterly and of the westerly disturbances were also found, at Point 

 Barrow as elsewhere, to be distinct and dissimilar. On further in- 

 stituting a comparison between the disturbance-laws at Point Barrow 

 and Toronto, it was found that although the laws of the deflections 

 of the same name at the two stations did not correspond, there 

 existed, on the other hand, a very striking and remarkable correspond- 

 ence between the laws of the easterly disturbances at Point Barrow 

 and of the westerly at Toronto, and between the laws of the westerly 

 disturbances at Point Barrow and easterly at Toronto. The corre- 

 spondence is traced in much detail, for the purpose of showing that 

 it is manifested, not in slight and unimportant particulars, but in the 

 most marked characteristics of both classes of phenomena. From 

 the correspondence in the hours at which opposite disturbance-deflec- 

 tions prevail, it follows, that the portion of the diurnal variation 

 which depends upon the disturbances, has opposite, or nearly 

 opposite characteristics at the two stations. 



In former papers the author considers that he has shown that, 

 for the purpose of obtaining a correct knowledge of the phenomena 

 of the regular solar diurnal variation, it is necessary to eliminate the 



VOL. VIII. 2 Y 



