14 REPORT—1857. 
On the Amount and Frequency of the Magnetic Disturbances and of the 
Aurora at Point Barrow, on the Shores of the Polar Sea. By Major- 
General SasBine, Jreas. R.S. 
Point Barrow is the most northern cape of that part of the American continent 
which lies between Behring’s Strait and the Mackenzie River. It was the station 
of H.M.S. ‘ Plover’ from the summer of 1852 to the summer of 1854, and to Cap- 
tain Maguire, now in the Section, and to the officers of that ship, they were indebted 
for the very valuable series of observations which he was now about to lay before 
the Section, and in part discuss. 
They were furnished with supplies of provisions, &c. for Sir John Franklin's 
ships, had they succeeded in making their way through the land-locked and ice- 
encumbered channel, through which they sought to effect a passage from the Atlan- 
tic to the Pacific. In this most dreary and otherwise uninteresting abode Capt. 
Maguire and his officers happily found occupation during seventeen months unre- 
mittingly, in observing and recording every hour the variations of the magnetic and 
concomitant auroral phenomena, in a locality perhaps one of the most important 
on the globe for such investigations. Their observatory, placed on the sand of 
the shore, which for a long tract nowhere rose much more than 5 feet above the 
sea, was constructed of slabs of ice, and lined with seal-skins throughout. The 
instruments had been supplied by the Woolwich establishment, together with the 
requisite instructions for their use; and the observations were made and recorded 
precisely in the same manner as those of the Colonial magnetic observatories. These 
were sent by Capt. 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 made in the Colonial observatories. 
The author then exhibited to the Section six diagrams, containing the results of 
this discussion, giving the reduced observations at each of the hours of the twenty- 
four. A sufficient body of the larger disturbances having been separated from the 
rest, it was found at Point Barrow as elsewhere, wherever similar investigations 
had been made, that in regard to the frequency of their occurrence, and the average 
amounts of easterly and westerly deflections, the disturbances followed systematic 
laws depending on the hours of solar time. The laws of the easterly and westerly 
deflections were also found at Point Barrow, as elsewhere, to be distinct and dissi- 
milar. The author explained how these observations were separated from the rest, 
for the purpose of this investigation. Upon instituting a comparison between the 
disturbance laws at Point Barrow and Toronto, it was found that the laws of the 
deflections of the same name at the two stations did not correspond ; but, on the 
other hand, that there existed a very striking and remarkable correspondence between 
the law observed by the easterly at Point Barrow and the westerly at Toronto, and 
between the law of the westerly at Point Barrow and easterly at Toronto; this 
correspondence was shown to exist not in slight or occasional particulars only, but 
throughout all the hours in well-marked characteristics of both classes of phenomena ; 
and from the correspondence in the hours at which opposite disturbance deflections 
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. The 
importance of eliminating these disturbances from the regular march of the solar vari- 
ation was then pointed out ; for when the diurnal variation is derived from the whole 
body of observations at Point Barrow, retaining the disturbances, the westerly ex- 
treme of the diurnal excursion, which, as is well known, occurs generally in the 
extra-tropical part of the northern hemisphere a little after 1 p.m., is found to take 
place at 11 p.m.; but when these larger disturbances are omitted, the westerly extreme 
is brought back to the same time as elsewhere, viz. 1 p.m. ; and the author suggested 
the probability that the anomalies which have sometimes been supposed to exist in 
the turning hours of the solar diurnal variation in high latitudes may be susceptible 
of a similar explanation. It appears, then, by a comparison of the Point Barrow 
and Toronto observations, that in the regular solar-diurnal variation the progression 
at the two stations is similar, the easterly and the westerly extremes being each 
reached nearly at the same hours, whilst in the disturbance diurnal variation this 
progression is reversed. Another distinction exists in their magnitudes, which are 
