insomuch that the line of no dip (which is commonly called the magnetic equator), does not agree exactly with the line of least intensity (or the intensity equator). And when we leave this neighbourhood, the inexactness of the law becomes yet more apparent, insomuch that in place of finding a pole of maximum intensity near the magnetic pole, we find two intensity poles in each hemisphere, each of either pair being far removed from the magnetic pole of the corresponding hemisphere. Thus of the two northern intensity poles, one lies in Siberia, nearly at the point where the River Lena crosses the arctic circle, the other lies a few degrees to the north of Lake Superior. Of the two southern poles, one lies in Adelie Island, the other near the antarctic circle, in about 120 degrees west longitude.

Observation has not yet satisfactorily determined the laws according to which the magnetic intensity at any place varies from time to time. We owe to Father Secchi, more than to any other observer, our knowledge respecting the diurnal and annual changes of the magnetic phenomena, though indeed this is a branch of science which has been enriched by the labours of a host of eminent observers. The regular diurnal variation of the needle may be thus described:-Remembering that when a needle is suspended horizontally, the northern extremity is farthest from the sun in the day-time and nearest to the sun during the night, we may speak of the needle's diurnal motion as of an effort of the end of the needle nearest to the sun to turn towards that luminary whether, he be above or below the horizon. Now, if the mean direction of the needle were due north, it is clear that the following changes would result from this law. At noon the south end of the needle would point due south, attaining a few hours later its maximum westerly excursion. At sunset (since both ends of the needle would now be equally distant from the sun) the needle would lie "north and south" as at first. A few hours later the northern end would attain its maximum westerly excursion, at midnight it would point due north again, and a few hours later it would attain its maximum easterly excursion. Lastly when the sun was due east the needle would point due north; a few hours later the south end would attain its maximum easterly excursion, and at noon would point due south as at first.

Remembering that at Paris the magnetic meridian is crossed by the sun about three hours before noon, and again about three hours before midnight, and further, that an easterly excursion

of the south end corresponds to a westerly excursion of the north end, we see that the following observations made by Arago correspond closely to the law stated above. "At about eleven at night in Paris (and the same law holds, mutatis mutandis, for all places in the northern hemisphere), the north end of the needle begins to move from west to east, and having reached its greatest easterly excursion at about a quarter past eight in the morning, returns towards the west to attain its greatest westerly excursion at about a quarter past one. It then moves again to the east, and having reached its greatest easterly excursion at half past eight in the evening, returns to the west, and attains its greatest westerly excursion at about eleven, as at starting." During all these changes the needle, as seen in London or Paris, is pointing far to the west of north, because while its westerly declination is upwards of twenty degrees, its diurnal excursions never exceed a quarter of a degree.

One important conclusion may be deduced at once from the peculiarities of motion just considered. The heating effects of the sun cannot be held to be the cause of the diurnal variation. If it were, we should find the needle's motion characterised by a single excursion to either side of the mean position, because the temperature has but a single periodic change per day. We have seen that there is a double excursion, precisely as though the sun's attractive force were concerned in producing the change. And, doubtless, though gravitation is not the cause of the needle's oscillation, a form of attraction resembling gravitation is the only sort of force to which the diurnal vibration can be attributed.

We find similar evidence when we come to deal with the annual changes in the needle's directive quality. For, in place of a maximum or minimum of disturbance in summer, we find that both hemispheres exhibit the maximum of magnetic disturbance at the same season, namely in January. And this epoch, as is well known, corresponds to the period of the earth's nearest approach to the sun.

But more singular than either the diurnal or annual changes of the magnetic action, are those variations in the amount of these changes which take place in a period of several years. It had long been noticed that in certain years the diurnal oscillations are much more marked than in others; and also that during years of greatest vibratory action the irregular perturbations of the magnet are also unusually large. But we owe

to General Sabine the discovery that there is a systematic process of increase and diminution, whose full period is somewhat more than ten years. Such a phenomenon would have seemed wholly inexplicable but for the singular accident that, at the very time when the observations were being made which resulted in the discovery of the period, another series of observations on a subject apparently altogether distinct from terrestrial magnetism were preparing the way for the detection of the real significance of the periodic changes we have referred to. Schwabe, the German astronomer, had undertaken the apparently useless task of counting day by day the number of spots on the face of the sun. Continuing his labours with an energy and patience that perhaps none but a German philosopher would have been capable of, he had after many years of persistent research, discovered that the spots become more and more numerous for a time, until they attain a maximum number, after which they gradually diminish, until at length the sun's face is wholly clear of them. He found that the period of this process of change is rather more than ten years. It occurred to General Sabine to inquire whether any relation exists between the ten year period of the solar spots and the period of the same length which he had discovered in the variation of the magnet's diurnal oscillations. He found that there is. When sun-spots are most numerous, the magnetic perturbations are most violent. Some ridicule was at first excited by the promulgation of the theory that this relation is not accidental; but subsequent research has not only confirmed the hypothesis, but has brought facts to light which leave us no room to feel any longer doubtful upon the subject.

The most remarkable evidence of the intimate association which exists between terrestrial magnetism and processes of change taking place upon the solar photosphere, is that which was afforded by the occurrence of a magnetic storm of unusual violence in 1859, immediately after the appearance of an intensely bright spot of light upon the sun's surface. It happened that two well-known observers witnessed the appearance of the bright spot, and its rapid motion across the face of the sun. Had the magnetic disturbance, which occurred during the next few hours, been the sole evidence of the sun's influence, some doubt might still have remained whether the coincidence were not simply accidental. But both observers recorded the exact epoch at which the spots appeared; and on a reference to the self-recording magnetic instruments of the

Kew Observatory it was found that at that very instant the indicator had been violently jerked, so that in place of the usually waved curve a sharply indented irregularity appeared upon the record-paper. The magnetic storm which followed was characterised by some very interesting features. Telegraphic communication was interrupted in many countries; in some places telegraphic offices were even set on fire by the intensity of the electric action; a flame of fire followed the tracing pen of Bain's telegraph; auroras of unusual splendour appeared in both hemispheres; and many other signs concurred to show that the whole frame of the earth had responded in intense magnetic thrills to the action-whatever it might have beenwhich had caused the sudden appearance of the swiftly travelling spot of brilliant light upon the solar surface.

Such phenomena as these lead us to recognise the real significance of the earth's magnetic habitudes. In dealing with the indications of the magnetic needle, in studying the changes which take place from day to day, from year to year, and from century to century in fixed observatories, in comparing the directive powers of the compass in different localities, and in watching the processes of change affecting the general aspect of the earth's magnetic habitudes during long intervals of time, we are in reality dealing with phenomena of cosmical importance. We may, in fact, look on our earth as an outlying observatory, whence we are enabled to watch the changes of the sun's magnetic action, and to determine the laws according to which it operates. Viewed in this light, the study of terrestrial magnetism becomes one of the most interesting and important which can occupy the attention of our men of science.

The Portrait in my Uncle's Dining-room.

CHAPTER X.

THE FARM AND THE FAIR.

"ON the Sunday which followed my visit to the Pinatels, François' wife did not make her appearance at church, nor did she go to her duties at Christmas. The Pinatels were certainly by no means fervent Christians, but still the women of the family were tolerably regular in their attendance at Church. I asked the widow why her daughterin-law did not come with her, and what she was doing at home. 'Nothing, as usual,' the woman answered. There she sits at the corner of the chimney, with her arms crossed and her feet in the ashes. If her petticoats happened to catch fire, I don't believe, Heaven forgive me, that she would stretch out her hand to put it out!' "I was in the habit of visiting the different families in my parish once or twice a month, according to what I supposed to be their need of spiritual advice or consolation, and only under exceptional circumstances broke through this rule. A fortnight therefore elapsed before I went again to the Pinatels. This time I found the young woman alone. She was sitting in the sun near the door of the house, her peasant's hat overshadowing her eyes, so that she only saw me when I was within a few steps of her. She seemed disagreeably surprised, and starting up suddenly, said in Provençal, There is nobody at home. They have all been out in the fields since morning.' I answered in French, ‘If I am not in your way, I will sit down and rest a little while.' She had probably fancied that I knew nothing of her former position, for she blushed and seemed surprised that I did not speak to her in the dialect of the country as I did to the other members of the family. But she soon recovered her self-possession, and with the air and manner she would have had in her mother's drawing-room, she said, 'Will you do me the honour to walk into the house?' I thanked her, but declined; and we remained seated on the bench outside.

"The weather happened to be wonderfully mild for the time of year. The birds hopped joyously amongst the bushes, and the little snowdrops were beginning to peep out in the sheltered spots under the hedges. 'What a beautiful day it is!' I said to the pale, stern young creature by my side. I always think this bright sunshine is like a look of love the love of a merciful God-on the works of His hand. The most deeply afflicted soul should be cheered by these benignant rays, which seem to give new life to all creation. We feel that God is our Father, and that He watches over us.' She did not answer, but looked at me in that sneering, offensive way which persons who have no religion always put on with Priests when they endeavour to suggest to them thoughts of faith, gratitude, and love of God. I had often met with this sort of contemptuous treatment at the hands of men imbued with the prejudices of philosophical intolerance, and I