own, and firmly believed that tree had not been described in it. To remove all doubts, and to give all possible sanction to what he advanced, Boerhaave immediately produced the work itself from his library, and, to his extreme surprise, found the tree fully described in it, with all its distinctive marks. Admiring the exact and enlarged knowledge of Linnæus in botany, in which he seemed even to excel himself, the venerable old man advised him to remain in Holland, to make a fortune, which could not escape his talents. (Stoever's Life of Linnæus.)

Boerhaave was not more remarkable for the extent of his medical and philosophical knewledge, than for his sincere and humble piety: in proof of which, need only be noticed a common saying of his, that he never saw a criminal dragged to execution, without asking himself, Who knows whether this man is not less blamable than I am?'

26.-OLD HOLY ROOD. See HOLY CROss, p. 220. 26.-SAINT CYPRIAN.

He was an African by birth, of a good family and well educated. He behaved with great courage and resolution in the Decian persecution, and openly invited the people to constancy and perseverance: this conduct so enraged the Pagans, that he soon fell a victim to their fury, and suffered martyrdom under Valerianus and Gallienus, in 258.

29.-SAINT MICHAEL.

Saint Michael was an archangel who presided over the Jewish nation, and had an army of angels under his command and conduct; he fought also with the Dragon or Satan, and his angels; and, contending with the Devil, he disputed about the body of Moses. See Rev. xii, 7; Jude 9. This festival has been kept with great solemnity ever since the sixth century. For customs on this day, see our former volumes. 30.-SAINT JEROME. Jerome was born in a town called Stridon, on the confines of Pannonia and Dalmatia. He translated the Old Testament into Latin: this version, now

styled the Vulgate, is the only one used or allowed by the Romish church. He died in the 80th year of his age, A.D. 422.

Astronomical Occurrences

In SEPTEMBER 1819.

THE Sun enters Libra at 56 m. after 9 in the evening of the 23d of this month, and on the 19th of which he will be eclipsed, but the eclipse will be invisible in this country; and he will rise and set during the same period as in the following

TABLE

Of the Sun's Rising and Setting for every fifth Day. September 1st, Sun rises 14 m. after 5. Sets 46 m. past 6

36

6

6th, 11th, 16th,

If the numbers in the following table be applied, as directed, to the time shown by a good sun-dial, it will give that which should be shown at the same instant by a well regulated clock.

Wednesday, Sep. 1st, to the time by the dial add 0 3 6th, from the time by the dial subtract 1 34

Monday,

Saturday,

Thursday,

11th,
16th,

Tuesday,

Sunday,

26th,

3 15

5 0

6 45

8 28

Moon's Passage over the first Meridian.

The Moon will pass the meridian of the Royal

Observatory at the following times, which will be convenient for observation, if the weather prove favourable: viz.

September 1st, at 57 m. after 9 in the evening.

Eclipses of Jupiter's Satellites.

The eclipses of Jupiter's Satellites which will be visible at the Royal Observatory this month, will be the following: viz.

EMERSIONS.

1st Satellite 4th day, at 0 m. after 1 morning.

12th,
19th,
28th,

9 evening. 11

2d Satellite 4th,

Other Phenomena.

Mercury will be in his inferior conjunction at 4 in the morning of the 7th of this month, stationary on the 16th, and attain his greatest elongation on the 23d. Saturn will be in opposition at half past 4 in the morning of the 21st; and Georgium Sidus in quadrature at 7 in the morning of the 14th. The Moon will be in conjunction with ẞ in Taurus at 35 m. after 2 in the afternoon of the 11th; with Pollux at 48 m. after 2 in the morning of the 14th; with Venus at 12 m. past 1 in the morning of the 19th; with Spica in Virgo at 4 m. after 2 in the

aftemoon of the 21st; and with a in Scorpio, at 11 m. after 2 in the morning of the 25th.

On the EFFECTS of GRAVITATION.

[Continued from p. 206.]

When one body is supported by another, the force of gravity causes it to press upon its support; if it be suspended by a string, this string is extended by the action of gravity exerted upon the body. This tension is also found to be wholly independent of the figure of the body; but in different bodies of the same kind of matter, or of the same density, it is exactly proportional to their bulks, and, consequently, to the quantities of matter they contain. Weight, and body or mass, therefore, though not synonymous terms, are always proportional to each other, at the same distance from the centre of the Earth, or rather the centre of terrestrial attraction. This limitation is necessary; for when bodies are removed either to a greater or less distance from the centre, the body or mass remains the same, while the weight, being the effect of gravity, is variable; and, consequently, the weight can be substituted for the mass only, when the situation with respect to the centre of attraction is the same. Since, however, it is known that the force of gravity varies inversely as the square of the distance, and the effect is always proportional to the cause, the weight of a body may readily be found at any distance either above or below the Earth's surface, when its weight at the surface is known. For since the centre of attraction is either in or very near the centre of the Earth, if r denote the terrestrial radius, h the height of the body above its surface, and w its weight at that surface, we have

(r + h)2 : r2 :: w :

r2w
=w';
(r + h)2

which expresses the effect of gravity, and, consequently, the weight of the body at the height h. If,

therefore, a body was found to weigh 100 lbs. on the shore of the Pacific Ocean, in the latitude of Chimborazo, and it was required to find its weight on the summit of that mountain, which is about 4 miles above the level of the sea; taking the radius of the Earth equal to 4000 miles, we shall have

99.8003 lbs. 99 lbs. 12-8048 oz;

and hence the loss of weight in consequence of this elevation is 3.1952 ozs.

Again, if it were required to ascertain the height at which a body that weights w at the Earth's surface would weigh only w', we should have from the preceding expression, in which h becomes the unknown quantity,

therefore

(†' + h)3w' = r2w,

If, now, it were required to find at what height above the Earth's surface a body would lose onefourth of its weight; by substituting these quantities in the preceding formula, we shall have

the height required. Consequently if r = 4000 miles

U