. Narrative of a journey to the shores of the Polar Sea, in the years 1819, 20, 21, and 22 [microform]. Scientific expeditions; Expéditions scientifiques. â â *-*mi»* No. IV. REMARKS AND TABLES CONNECTED WITH ASTRONO- MICAL OBSERVATIONS. DIURNAL VARIATION OF THE MAGNETICNEEDLE. The Tables Nos. IV., V., VI., contain the monthly averages of a series of mean diurnal variationH ; the two first iiave been deduced from the preceding Tables, Nos. I. and II., and the third from observations on the position of the needle at Siave Lake, which, in consequence of their length, are not inseited in this w
. Narrative of a journey to the shores of the Polar Sea, in the years 1819, 20, 21, and 22 [microform]. Scientific expeditions; Expéditions scientifiques. â â *-*mi»* No. IV. REMARKS AND TABLES CONNECTED WITH ASTRONO- MICAL OBSERVATIONS. DIURNAL VARIATION OF THE MAGNETICNEEDLE. The Tables Nos. IV., V., VI., contain the monthly averages of a series of mean diurnal variationH ; the two first iiave been deduced from the preceding Tables, Nos. I. and II., and the third from observations on the position of the needle at Siave Lake, which, in consequence of their length, are not inseited in this work. Table IV. was extracted from Mr. Hood's Journal, where it is accompanied with these remarks : â¢* The following table contains the mean diurnal variations of the compass for four months, at Cumberland-House. Many unavoidable interruptions prevented the number of days in each month from being complete, and some irregularities have been caused by the motion of the compass box. Those days are not included on which the needle was affected by the Aurora. As in other places, the diurnal varia- tion increases with the advance of summer, and the needle reaches the extremes of variation at nearly the same hours. But the maximum is at the coldest period, and the minimum at the warmest, which is the reverse, I believe, of the observations which have been made in Europe and in the East ; Table V. is an abstract of my observations on the positions of the needle at Fort Enterprise (contained in Table II.) which have been reduced to the variation shewn by the same needle, on September 4, 1820. In Table VI. the positions of the needle observed at Moose-Deer Island, in 1822, have been reduced to the mean variation obtained at that place in July, 1820. It should be remarked, that the whole of the observations made on the positions of the needle at Fort Enterprise and Moose-Deer Island, have been used in forming the Tables V. and VI. The appearance of the Aurora, and the
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