By this table we observe, that on the days of the new and the full moon it is high water at London about 3 o'clock; and as the tide requires some time to make its way up the Thames, we find high water occurring the earlier as we go down the river, for at Greenwich the tide is at its height about 40 minutes past two, and at Gravesend so early as half an hour past one. The period of high water at the island of Alderney, at Southampton, &c being marked O H. 00 min. points out that the tide there is full about mid-day and mid-night.

- The height to which the tides rise in the great oceans it is difficult to ascertain for want of proper land-marks by which to measure its elevation: but in many parts where the currents are confined in their course, the difference between the full and the ebb is very considerable: thus along the coasts of Britain and Ireland the highest tides rise in general from 10 to 15 feet: but in the mouth of the Severn they rise much higher; on the coast of the island of Jersey spring tides flow from 30 to 40 feet; and in the bay of Fundy, between Nova Scotia and New Brunswick, they attain a height of from 50 to 70 feet.

In the introduction to the treatise on Geography, (pages 7 and 14 of this volume) it was observed that, by the rotation of the earth on its axis, the phænomena of light and darkness conftituting what we call a day were produced; that had the earth's axis been placed perpendicularly on the plane joining the earth and the sun, the globe would have been illuminated by the sun's rays constantly in the same manner all the way from the north to the south pole, and the days and nights produced from the earth's diurnal revolution, by which all parts of its surface are successively exposed to his light, would have been constantly of the same

length

length throughout the year;-that in such a state of things no sensible variation in the quantities of heat and cold constituting that interchange of seasons we now experience, especially in regions remote from the equator, would have been perceived; but that from the oblique position of the earth's axis with respect to her orbit arise the regular changes in the length of the day and the night, and in the degree of heat and cold by which the seasons are so happily diversified and characterised.

The earth in her annual course round the sun describes a path called the ecliptic, which if observed from the sun would appear to pass by certain fixed stars or clusters of stars if parallel to this path or line be drawn two other circles, one on each side at the distance of 8 degrees, a band or zone in the heavens will be determined in breadth 16 degrees, within the limits of which not only the earth but all the other planets hitherto discovered and our moon will describe their course. This zone passing through a number of constellations or clusters of stars, chiefly named after some animal, has hence been called the zodiac, from a Greek term fignifying a living being or animal. These constellations are twelve, and usually styled the signs of the zodiac: their names and the characters by which they are designated are the following, viz.

Of these signs the first six are called the northern signs, as lying in that portion of the ecliptic which is situated on the north side of the equator, and the remaining fix are called the southern signs, as lying on the south side of the equator; each sign being the 12th part of a great circle or of 360 degrees will contain 30 degrecs.

In fig. 2d of Astronomy let the ellipse ECLP represent the plane of the Earth's orbit described by her annual motion round the sun. It has already been said that this plane is inclined to that of the earth's cquator, intersecting it at an angle of 23 degrees 28 minutes 10 seconds: and that consequently the axis on which the earth performs her daily rotation being perpendicular to the plane of her <quator must be inclined to the plane of her orbit or of

the