and mind, and her sons, looking forward to her speedy death, were anticipating the acquisition of a valuable servant. She has always declared that when she dies Peter shall be free, only asking of him maintenance during her lifetime, and it is understood that she has made a will setting him free at her death. Her sons are jealous of the interest manifested for Peter by his new friends, and, doubtless calculating on obliging her to make a new will, made great opposition to his leaving the neighbourhood and placing himself under our protection.

'We were to assemble at some distance east of Cumberland, and I sent up one of the young men to bring Peter down, with directions to make such arrangements for the comfort of his old mistress as would enable him to stay away some time. The old lady was almost bedridden, and had been so badly taken care of at her son-in-law's, that Peter had found it necessary to place her among strangers, who resided some sixty miles west of Cumberland, and he was accompanied on his visit to the old lady by our young man. They had to pass through the neighbourhood where her sons reside, and we did not know what effort might be made to detain or arrest Peter. It was therefore thought advisable that he should be under the protection of some white person.

This visit being accomplished, and everything done that was necessary for the old lady's comfort, Peter joined us all in camp and resumed his old work, very desirous to show his new attainments in French pastry and boned turkey.

'Last winter was very severe, and living in tents in this mountain region from November until April, has required stout hearts and stout limbs, and several of those who began the campaign with us were forced to abandon the survey. One man in particular was confined to his bed several weeks by rheumatism, refusing to go home or to be lodged in any of the neighbouring houses, insisting on being kept with the party, and depending entirely on Peter for medical advice and nursing. Peter nursed him with all the tenderness and kindness of a woman, and aided by this care, and by his own stout spirit, the young fellow ultimately recovered, and served out the campaign. It was during the hardships of last winter that Peter's full value was learned. Though perhaps the most delicate man in the party, he was always up to his duty, had breakfast every morning before daylight, waiting on twenty men with unceasing care, and perhaps he is the only cook in America who could have kept so many hungry mouths going with hot buckwheat cakes.

'Our winter campaign ended in April, and we all went back for six weeks to Baltimore; Peter being indulged with a visit to his old mistress, with a white body-guard to protect him. Our present party has been in the field only three weeks, and several of the men have never before served with Peter; but he seems to be as usual making friends among us.'

Here Mr. Blake's narrative ended, but as I may find no better opportunity of relating the particulars of Peter's subsequent history, I will not quit the subject without telling all I know of it.

Peter served with us that year most faithfully, and when the winter came, went with us down to Baltimore. It was considered unsafe for him to be left in the neighbourhood of the family of his old mistress, and employment being found for him, he remained in Baltimore till the death of Mrs. R- when it was ascertained that the plans of her sons had succeeded, and that she had been induced to revoke her former will, and to make a new one, leaving Peter to one of them. It was also ascertained that this man was making an effort to get possession of his wrongfully-acquired property, and Peter's friends therefore advised him to place himself beyond reach of legal process. Means were furnished him for reaching Boston, and letter provided, introducing him to some of the most respectable persons in that city. For a long time he was terribly home-sick and pined after his old haunts and his young masters. He had always been a member of the Episcopal Church of America, and in Boston he attached himself to the Church of the Advent, in those days considered the most high church' Church in New England. He became well known as a renovater and repairer of men's clothes, was very comfortably off, and had several men who worked under him. He never married, and died shortly before the Civil War. Several times he visited Baltimore, with due precautions, where he stayed in the house of the chief of the old survey, and was welcomed and made much of by his former friends. In Boston, his Rector, and the Church to which he united himself, greatly esteemed and respected him. But perhaps the strongest testimony to the blameless consistency of his Christian character lies in the fact that of the young men composing the parties with whom he worked, all, so far as I have been able to ascertain, became after a while, men who served God in their generation, and trace their first religious yearnings to their intercourse with Peter.

THE MOON AND THE EARTH:

THEIR PAST AND FUTURE HISTORY.

BY REV. HENRY N. HUTCHINSON, B.A., F.G.S.

PROFESSOR G. H. DARWIN (of Cambridge) and others have recently made some very interesting researches on the subject of tides. The results of their labours are of a new and startling character. By means of experiments and abstruse calculations, which only accomplished mathematicians can follow, these scientific seers—if we may so call them have been enabled to interpret, from facts which to us convey very little meaning, the past history of our earth and moon; and also to present us with a glimpse into the future, which cannot fail to be of universal interest. We all live on the same planet, though we shall never see the state of things which must some day come to pass; yet we cannot but listen with interest to those who are able, to some extent, to satisfy our natural curiosity about the future. The results arrived at also give a new and deeper interest to that daily phenomenon of the ebb and flow of the tide, with which most of us are familiar. To the ancients that daily ebb and flow was for many ages a great puzzle. The connection between high tides and a new or full moon was long ago perceived by Pliny and Aristotle, but they could not understand how the tides were caused. This we now know; but it is only of late years that we [have realised the great power they possess of regulating the movements of our planet. They are found to exercise a controlling influence upon day and night, the seasons, and perhaps even the weather.

It now appears that not only has the moon for ages and ages been producing tides on the earth, but that in days gone by the earth produced powerful tides on the moon! Nor must we leave out of consideration that great centre of our system called the sun, which, if he were nearer, would have a very powerful effect, but being a long way off, while the moon is quite near to us, his pull upon the earth and its watery envelope is very much less than that exerted by the moon. We may therefore leave solar tides out of consideration for the present, and examine those of the earth and her satellite. The earth rotates on its axis once in very nearly twenty-four hours, while the moon revolves round the earth in twenty-seven days, and takes exactly the same time to rotate once on her axis. This is why

she keeps the same face always turned towards the earth. If any one does not believe that the moon rotates on her axis, let him just try and walk round the table, on which we will suppose a lamp to have been placed. He will soon find that, in order to keep facing the globe of the lamp, it is necessary to effect a slight rotatory movement while going round the table, and by the time he has gone once round he will have faced successively all the four walls of the room; that is, he will have turned round once on his own axis. The popular explanation of the tides is that as each portion of the earth and its ocean in spinning round come under the moon they are lifted up by her attractive influence. A protuberance is thus made; but it does not last long. It soon begins to drop, for it is now being carried away to the west, and therefore ceases to be under the moon. In this way a tidal wave is formed, some parts of the earth and ocean being gently drawn up, others as gently subsiding. A similar protuberance is caused on the other side of the earth; the water on that side being less pulled up than the earth underneath it. Hence there are always two protuberances travelling round the earth at a distance of 180° from each other. It is clear, therefore, that the movement of the tides is partly due to the earth's rotation on its axis. Stop that rotation and they cease to travel, that is, the tides practically cease. The protuberances would be there, but we should not be made aware of their existence. It may be new to some that there are tides in the solid earth as well as in the ocean; but it is an undoubted fact. Sir William Thomson has shown that if the earth were quite rigid and unyielding the ocean tides would be much greater than they are, and that what we see is the excess of the ocean-tide over the land-tide. He has also drawn some other important conclusions from this yielding of its crust to the pull exerted by the moon with regard to the state of the earth's interior. Professor Darwin has shown that the moon once belonged to the earth. The two rotated as one mass. But owing to the centrifugal force of the outer portion, and also to the continued daily throb of the solar tide, the outer and lighter portion was partly thrown and partly pulled off. Being in a semi-fluid, or viscous state, it assumed a spherical shape-as its parent did before it. The pull of the earth was too strong to allow it to fly away into space, and so it was forced to begin revolving round its parent. In this way, then, solar tides (tides caused by the sun) had a good deal to do with the birth of the Both were very hot, and consequently unfit for vegetable or animal life; but they have had plenty of time to cool since then, and the moon seems to have cooled more rapidly. It is almost a cold body, so far as we can tell with instruments for detecting rays of heat. Being smaller, it naturally would cool more quickly. Now at this period Professor Darwin calculates that the moon went round the earth in about three hours. It also made one rotation on its axis in that time. The earth's day, or period of rotation, was also VOL. 20.

moon.

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the same. The moon kept, as now, the same face towards the earth. But this state of things, he says, could not last. It was not a stable condition of affairs; and as a man who has lost his balance must fall, so the moon must either have gone back to the earth to be reabsorbed, or it must have begun to retreat. Our satellite was somehow so influenced that she decided on the latter course, and retreating she has been ever since. At the same time, both bodies began to slacken their rotation, the moon more so than the earth. What follows from this? Clearly it follows that the tidal protuberances made on the moon by the earth's attraction must begin to travel round the moon (because she was rotating more slowly, and not keeping the same face to the earth). In other words, tidal waves were started on the moon. She was too hot then for an ocean of water to exist on her surface, and so these tides were land-tides, or upheavals of the solid or semi-fluid mass of the moon; but that does not affect the argument. The tidal wave must have caused friction, and friction would tend to diminish the rate of rotation, just as when you put the break on to a carriage wheel. And so these tides, caused by the earth's pull, acted like a break on the moon, and retarded its rotation. This went on for ages, until the rotation became so slow, that at last it took the moon twenty-seven days to make a single rotation.

This, then, is what the earth has brought the moon to. But the action has been mutual. The moon, by way of revenge, has been steadily acting in the same way on her parent. A similar friction of tidal waves produced by the moon has been for ages lengthening the terrestrial day, until from three hours it has grown to 23 hours 56 minutes 4 seconds. Thus the parent acts on the child and the child on the parent. It has even been found possible to calculate roughly the time during which these changes have been taking place. Professor Darwin put it down at about fifty-seven millions of years. But he has also attempted a glance into the future, which tells us that this tidal retardation,' as it is called, will go on until, in about 150 millions of years from now, the length of the day will be 1400 hours! But whenever this state of things is reached the moon's day and month will also be 1400 hours, and in that case tides would cease. This state of things will be more permanent, and would last for countless ages, were it not for the influence of the sun. Solar tides, or tides caused by the sun, must then begin to make their influence felt, and that influence would also be a retarding one. So the earth and moon would not be left in peace to keep things as they had mutually arranged. An endless series of complications would be introduced, into which we need not enter further than to say that probably the earth's rotation will be so much further reduced that the day and the year will be equal. After that, if the world lasts long enough, rotation must cease altogether. This would cause a sad state of things, for in that case there would be no seasons, but only a six-months day and a six-months night! This is a