bodies, has supplied an admirable substitute. For this purpose, the angular distance that the moon will be from the sun, or from some particular star, every third hour of the day and night, is calculated with great exactness, and published in the “Nautical Almanac." The mariner has only, therefore, to measure the distance between these two bodies, and, by looking for the hour when a corresponding distance would take place by Greenwich time, he can determine his difference of longitude from that meridian by the difference which exists between the time of his observation and the computed time already mentioned.

A more beautiful application of the phenomena of the heavens to the uses of man it would be difficult to discover, or one exhibiting greater skill, accuracy, and profound depth of calculation. I have here merely given the principle on which this calculation for longitude is based, leaving out the various practical difficulties which would only tend to render the subject too complicated for admission in this elementary work.

The rapidity of railroad travelling brings these variations of time, occasioned by difference of longitude, very prominently into view on those lines running in an east and west direction. A traveller on the Great Western railway would find that his watch, which was correct on his leaving London,

would, on his arrival at Exeter, be about fifteen minutes in advance of Exeter time, he having traversed nearly four degrees of longitude; and were the clocks on the line regulated by local time, the difference between them and his watch would mark his progress to the westward, every four minutes of difference shewing a degree of longitude. Railway clocks are, however, now generally regulated by Greenwich time, as the variations between the different stations would otherwise cause much difficulty and confusion. To remedy the inconvenience resulting from the railway clocks differing from the local time, some have lately been constructed with two hands, the one shewing Greenwich and the other local time; the difference between the two hands being the difference of longitude in time, or the time it would take for the earth to turn that portion of a revolution comprised between these two places.

Were two travellers to set out from London on a voyage round the world, the one traversing the globe from west to east, and the other from east to west, the one who travelled to the east would gain a day by the time he had circumnavigated the globe, he having by his own movement round the earth made one revolution more than the earth itself, consequently producing one more rising and setting of the sun than had he remained stationary; whereas

the traveller who went towards the west would lose a day, he having by his own movement, in a contrary direction, made one revolution less than had he remained at home. The days of the former would each have been shortened, by as much as he advanced in longitude, in time every day; and the days of the latter would be lengthened in a similar manner. When they had both completed their journey, and met again in London, the one would call it Monday, the other would affirm it could only be Saturday; at the same time the chiming of the bells, and the quiet diffused over the busy world on that happy day of rest, would clearly indicate that both were in error, and that it was Sunday: the assistance of the philosopher would be required to blend all these seeming inconsistencies, and to account for them on scientific principles.

We here behold what labour and calculation has been required to enable the mariner to direct his course from shore to shore; and yet we find the feathered wanderers of the sky winging their way from one continent to another without chart or compass to direct their track, and yet with a certainty and precision that seems to mock the more laboured efforts of the mind of man. To account for this extraordinary faculty implanted in them by their beneficent Creator is beyond our power. We can only behold in it a further proof that to every creature

has God awarded instincts according to their several wants and necessities; and it should teach us to rely, with still firmer confidence, in Him who hath so carefully provided for the wants of all His

creatures.

CHAPTER X.

THE SEA-SHORE.

"And thou, vast Ocean, on whose awful face

Time's iron feet can print no ruin-trace;

By breezes lull'd, or by the storm-blasts driven,

Thy majesty uplifts the mind to heaven."-MONTGOMERY.

THE last two chapters having directed our attention to the sea and nautical affairs, we will now extend our inquiries along the coast, and examine some of the wonders which old Ocean is constantly performing.

The beach on which we walk, strewed with pebbles round and smooth almost as marbles, tell of the many ages that must have elapsed since those stones were once a solid rock. One may here trace the first opening crack or fissure between the severing mass and the parent stone, how from time to time the constant but imperceptible flow of the waters widened the opening, till at last the fragment became entirely disconnected. The same constant influence,