The accompanying drawing represents the seed and its appendages, more or less magnified.

Explanation of the Figures in Plate I.

Fig. 6. The two valves of the glumaceous perianth, with the stiff hairs, the spine and articulated awn.

7. The grain, with part of the skin torn at the base, to shew the albumen, of which nearly the whole is composed, the cotyledon

and the embryo.

8. The seed, with a fourth part of the awn, to shew its form when ready to separate from the spike.

9. The same, as it appears some hours after separation.

Account of the Observations and Experiments made on the Diurnal Variation and Intensity of the Magnetic Needle, by Captain Parry, Lieutenant Foster, and Lieutenant Ross, in Captain Parry's Third Voyage, with Remarks and Illustrations. By PETER BARLOW, F. R. S. Mem. of the Imperial Academy of St Petersburgh, &c. (With a Plate.) Communicated by the Author.

As the experiments referred to in the head of this article were

performed under such extraordinary advantages of locality, of

at the base in a reversed cone, which is very sharp, and covered with stiff hairs directed upwards, so that when the point penetrates into any substance, the hairs not only prevent it from coming out, but contribute to make it go deeper. M. Desfontaines, in his Flora Atlantica, and M. Lamarck in the Encyclopedie, have pointed out the inconveniences to which a seed so organised subjects travellers passing over the fields of Barbary, Greece, and Portugal, at the time of ripening of the stipas. The seed penetrates into their clothes, and sooner or latter disconveniences them in a high degree, by producing scratches of various depths upon the skin. A great mortality of the cattle, which took place in 1823, in the neighbourhood of the village of Berczel in Hungary, afforded an opportunity to the Professors of the Royal University of Pesth, of making known a still more singular effect produced by these seeds. It was found that the seeds of the stipas, which abound in the pasture grounds of Berczel, stuck to the wool of the sheep, penetrated into the skin, and even made their way to the internal organs. On dissecting a great number of these sheep, seeds were found in the vicinity of the liver and in the peritonæum, and the skin, examined between the eye and the light, had the appearance of a sort of riddle. As these grasses occur in all the south

instruments, and of observers, they cannot fail to be highly interesting to every one who has paid attention to this curious and important branch of natural philosophy. With regard to locality, no place could have been more admirably situated than Port Bowen, in latitude 73° 14′ N., longitude 88° 54′ W., with a dip of 88° 1′, and consequently within a very short distance of the magnetic pole, and yet sufficiently remote to leave to the needles a natural directive power, which they would in all probability have lost, had the approximation to the Pole been much greater. With regard to instruments, every thing that could be effected by the skill of the most distinguished artists in London, was liberally supplied to the expedition by the Government; and as observers, it is sufficient to mention only the names of Parry and Foster, as they cannot fail to inspire us with every possible confidence, both with respect to the accuracy of the observations, and to the most careful and unbiassed registry of the results. It is but fair, however, to state, that these two distinguished individuals alone, would not have been able, with all the zeal they are known to possess, to have obtained such a series of results as those to which we are now referring. It was necessary for this that they should be seconded by the cordial assistance and co-operation of the other officers of the expedition. This assistance was cheerfully given; and it is acknowledged in the most handsome and liberal terms by the authors of the memoir in which these experiments are recorded, and which has been recently published as a separate part of the Transactions of the Royal Society for 1826.

The experiments commenced about the 10th of December 1824, and were continued to the end of May 1825; and, when we consider that, for a considerable part of this time, the sun was below the horizon, that the thermometer was sometimes 40° below zero,—that the place of observation, a snow house,

ern parts of Europe, the above fact ought to fix the attention of the agricul turists of those countries. The stipe do not furnish good fodder, and the meadows would lose nothing by their absence. If they could not be extirpated all at once, the flowers are surmounted by an awn upwards of a foot long, by which they might easily be plucked off, before detaching themselves spontaneously. Should a seed happen to have buried itself in the substance of the skin, it would require to be extracted by the ordinary means, for accidents of this kind are not to be remedied by a more complicated treatment."

was at a distance from the ships, in order that the needles should be out of the influence of the iron on board; and that, notwithstanding these obstacles, the needles were carefully watched, the experiments performed, and the results carefully registered every hour, and frequently oftener, during this whole period; we shall feel convinced, that more than common exertions were made, and more than usual interest must have been excited, in the pursuit of these curious and valuable experiments; and, if we add to this, that these energies and these means were employed in a situation where Nature has placed her great depot of magnetic powers, and where every phenomenon of this kind is exhibited on the grandest scale, we shall then, and not till then, sufficiently appreciate the value of these interesting and important results.

With this feeling, I have thought that a brief abstract of these experiments would be acceptable to many of the readers of the Edinburgh Journal, particularly to those who have not the opportunity of consulting the original memoir; and I have accordingly, in the following pages, endeavoured to convey within the least compass, a general view of the subject, and have ventured also upon one or two illustrations of some of the theoretical points touched upon by the authors of the papers in question.

The first of the magnetic articles is by Lieutenant Foster, from which it appears, that, previous to his leaving England, he had determined upon making a series of observations on the daily variation of the magnetic needle, when any opportunity offered of so do`ing; and the first occurred at Whale Fish Islands, during the time of trans-shipping the stores from the transport which had accompanied the expedition to that place. The time employed in these experiments was only three days, consequently the results are not so certain as we could wish; but it is satisfactory to find, that the few facts which were obtained agree remarkably well with each other, both as to quantity and to the time of the day when the variation was the greatest westerly, the least westerly variation, or the maxi mum of easterly variation, occurred during the night, and was not observed. The greatest daily variation westerly was 23', and this occurred at 1h 10' r. M., at which time the sun was west by compass, the mean variation being 70° 2′ W., and dip 82° 53′ W. The important remark, distinguished above by italics, seems to have been a strong incitement to Lieutenant Foster to prosecute the subject again on a larger scale the next favourable opportunity, which did not occur till the ships were laid up for the winter at Port Bowen. At this place, as we have already stated, the experiments were begun on the 10th of December 1824, on one needle only. In the

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 Im 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,

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.

66

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.