course of this month, however, the varied phenomena which this one exhibited, while every thing besides appeared to partake of the stillness and monotony of this dreary region where it was posited, excited that degree of interest amongst the officers of the expedition which we have endeavoured to describe; and with the new year commenced a much more extended series of experiments on the daily variation, the variation of intensity, and, in fact, of the whole series of which it is intended to give a general outline in the subsequent pages.

The detail of the daily variation experiments forms the second of these articles. After describing the needles employed, marked No. 1. and 2., and a third, employed exclusively for determining the changes of intensity; and also acknowledging the assistance of Lieutenants Sherer, Ross, Messrs Crozier, Richards, and Head, as also that of Mr Hooper for the delineation of a very accurate diagram", offering a graphical exhibition of the several changes; the authors proceed to take a sort of general review of their results, as follows:

"Soon after the observations were commenced, it was ascertained that, twice in every four and twenty hours, the needles moved past a certain point, which may be denominated the zero, or mean magnetic meridian; a fact which was first rendered clearly apparent from the accompanying diagrams, already mentioned, by which it appears, that, in every instance except one, both needles every day passed the line in question. On a single day, February 24, the needle No. 2. did not arrive at it during its eastern motion.

"The means of the times of the needle passing this zero, as deduced from four months' continued observations, is 6 hours 15 minutes A. M., and 4 hours 37 minutes P. M., the mean time in each month being as follows:

To avoid the insertion of many useless figures in the tables, the resulting amount of easterly or westerly deflection on each side of the zero has been computed.

The maximum westerly variation at Port Bowen, appears from these observations generally to have occurred between the hours of 10h A. M. and 1m P. M., the mean result of 120 days' observations being 11h 49m a. M. The minimum westerly variation, or the greatest deflection of the north end of the needle to the eastward, took place between 8h P. M. and 2h A. M., the mean time deduced as above being 10h 1m P. M.

* In order to give an idea of this diagram, we have given a sketch of it in Plate V., for six days, viz. from the 20th to the 26th of March,

PLATE V.

Edin new Phil. Jour.p..

In a few instances the maximum deflection of the needle to the westward occurred as early as 8h A. M., and as late as 3h P. M.; and, in the like manner, the greatest deflection eastward took place at 2h and 3h P. M., on some few occasions. In all these anomalous cases, however, it was remarked, from simultaneous observations on the times of vibration of a suspended horizontal needle, that these irregularities were evidently due to an extraordinary alteration in its intensity, which produced a deflection contrary to the regular order of the motion of the needle.

The diurnal change of direction appears, by these observations, to have been seldom less than one degree, and sometimes to have amounted to five, six, and even seven degrees; and there can be no doubt, that the changes in this amount were more or less due to the position or influence of the sun, and probably of the moon, on the terrestrial magnetic sphere; but the particular law of this influence is a question of great delicacy, and of intricate research, and will be best left to the investigations of those who are theoretically conversant with these subjects.

After these general observations, the tables to which they allude follow; these, however, occupy forty quarto pages, and, of course, we can only attempt a general explanation of them; they are given under the following title.

"Tables, shewing the observed daily variations of the horizontal needle, from 10th December to 31st December 1824; and from 1st January to 31st May 1825, at Port Bowen. Lat. 73° 14' N., long. 88° 54′ W. Mean dip 88° 1.4 N., and mean variation 124° W."

After 1st January, when the general series commenced, these tables exhibit the deflection of the two needles No. 1. and No. 2. for every hour, and frequently intermediate observations, to the end of ́the series, with the registered temperature at the moment of observation; but, as I have already observed, they are too extensive to allow us to attempt a regular detail of them.

Lieutenant Foster has, however, in a subsequent article, given a general abstract of the five months' observations, and this, by a little farther abridgment, will reduce them to such a compass, as to allow of their being inserted in the pages of the Journal. Here we have given only the greatest amount of the daily variations for every day, and the hours and minute when the needle had its greatest and least westerly bearing; or the time of maximum westerly and easterly variations; the temperature at those times; the state of the winds and weather, with a column, also indicating whether the aurora boreales were, or were not, visible. These tables will be sufficiently intelligible, with one remark, namely, that, in the column marked A. M., the hours sometimes exceed twelve, and ought, therefore, to have fallen in a column marked P. M.; but, to save room, we have preferred the above notation, which will be understood to indicate the hours since midnight. The same occurs in the column of maximum easterly bearings, marked P. M. Here the time indicates the hour, &c. past noon.

ABSTRACT of the Daily Variation Experiments on Magnetic Needle No. 2. from January 1. to May 31. 1825.