consideration, because the calculations from the solar tables give the apparent places of the sun, or its longitude with the effect of aberration included, and therefore always about 20m too little. But from this observation a conclusion will follow very different from that which the objection supposes. The retardation mentioned, is properly the time that the calculated phases of a transit of Venus will precede the apparent phases, supposing the tables, from which the calculation is made, to give the true places of the sun. If they give the apparent places of the sun, this retardation, instead of being lessened, will be considerably increased. In order to prove this, it may be remembered, that in deducing, by trigonometrical operations, the geocentric places of a planet from the heliocentric, the earth is supposed to be in that point of the ecliptic which is exactly opposite to, or 180° from the place of the sun, and that this supposition is just only when the sun's true place is taken. In reality, the earth is always about 20" more forward in its orbit, than the point opposite to the sun's apparent place; and in consequence of this it will happen, that in calculating a transit of Venus, from tables which give the sun's apparent places, a greater difference will arise between the calculated and the observed times, than if the tables had given the sun's true places.

For, let s be the sun, T the earth, v Venus. Were there no aberration of light, the sun place, or in the direction Ts. aberration, it will be seen 20" the direction Ts, supposing STs to be an angle of 20". Now a calculation from tables giving the true places of the sun, would not be the time of the observed conjunction, to the time that Venus gets to Ts; but this, though the time of the true conjunction, would not be the time of the observed conjunction; for the sun being then really seen in the direction Ts, Venus, after getting to Ts must move 20", or from a to c, before the apparent conjunction can take place.

would be always seen in its true

But, in reality, in
But, in reality, in consequence of

less advanced in the ecliptic, or in

E

T

But if the calculations are made from the apparent places of the sun, the conjunction will be fixed to the time Venus gets to t s, or a line drawn through s parallel to s T; for in this case t will be the point of the ecliptic opposite to the apparent place of the sun, and the longitude of the sun seen from will be 20" less than its true longitude, and therefore the same with its apparent longitude. But the earth being then really at T, Venus will, at the calculated time of a conjunction, be observed at a distance from the sun equal to the angle This angle, supposing vт 277, and vs 723, may be easily found to be 72".2. Add to this 3.7, the proper aberration of Venus at the time of a transit, removing it more towards E, and the whole visible distance of Venus from the

LTS.

1

sun's centre at the calculated moment of a conjunction, will be 75".9, over which it will move in 19 minutes of time. And this, consequently, will be the retardation of the phases of a transit of Venus occasioned by aberration, on the supposition, that in calculating, the sun's apparent, and not his true place is taken.

In a postscript to this letter Dr. P. says: in a former letter, I gave, by mistake, the error occasioned by aberration, less than I have now given it. The discovery of this mistake I owe to the kind assistance and correction with which Mr. Maskelyne, the astronomer royal, has been pleased to favour me. I have, for the sake of more distinctness and clearness, supposed Venus to move in the plane of the ecliptic. Some differences will arise from the inclination of the path of Venus to the ecliptic, and also from taking the aberration of the sun, and the proportion of Venus's distance from the earth to her distance from the sun, exactly as they really are at the time of a transit. Thus, at the time of the last transit of Venus, supposing light to come from the sun to the earth in 8m.2, the aberration of the sun was 19.8. The distance of Venus from the earth was to its distance from the sun as 290 to 726, and therefore the retardation 18m 16. Mr. Canton has observed, that in the Con. des Temp, Mr. De la Lande makes the effect of abberration, at the inferior conjunction of Venus and Mercury, to be an augmentation of their longitudes. Indeed, Mr. Bliss himself observes this; and yet through an oversight, makes the effect as to time to be an acceleration. Vid. Phil. Trans., vol. 52, p. 249.

XLVIII. A Catalogue of the Fifty Plants from Chelsea Garden, presented to the Royal Society by the Co. of Apothecaries, for the Year 1769, pursuant to the Direction of Sir Hans Sloane, Bart. By Wm. Hudson, F. R. S. p. 541. This is the 48th presentation of this kind, completing to the number of 2400 different plants.

XLIX. A Short Account of the Observations of the late Transit of Venus, made in California, by Order of his Catholic Majesty, by Don Vincent Doz. Communicated by his Excellency Prince Masserano, Ambassador-from the Spanish Court, and F. R. S. p. 549.

Don Vincent Doz, commander of a Spanish frigate, is just arrived at Madrid. He brought with him, and presented to the king, an account of his observation of the last transit of Venus at California, whither he was sent last year for that purpose, being in substance as follows:

The latitude of the village of St. Joseph, 8 leagues distant from Cape St. Lucar 23° 5′ 15"; the longitude from the meridian of Paris 7b 28m 174; the two internal contacts of the planets were at 17m 25, and at 5h 54m 441. Hence,

on the computation of Mons. Pingré, in his Memoir of the year 1767, the solar parallax is 8". And the distance of the sun from the earth is greater than it was supposed to be, or nearly 6,685,000 leagues.

L. Extract of a Letter, dated Paris, Dec. 17, 1770, to Mr. Magalhaens, from M. Bourriot; containing a short Account of the late Abbé Chappe's Observation of the Transit of Venus, in California. Translated by Dr. Bevis, F. R. S. p. 551.

The 7th of Dec. inst. the journals and Mss. of the late Abbé Chappe were deposited at the Royal Observatory, with M. Cassini de Thury, by the Sieur Pauli, one of the king's engineers and geographers, who had accompanied the Abbé in his voyage to California. M. Pauli relates, that M. Chappe chose to stay at St. Joseph, a small village 10 leagues from St. Lucar, though the contagious disease prevailed there, and relying on his own good constitution, because he had no more than 8 days to prepare for his observation.

Eight days after the transit, he sickened, yet continued his observations to the 18th of July; and, a little before his death, left his materials in writing, put into a box, with M. Pauli, to be delivered to the Royal Academy. He died about the 1st of August, as did, about the same time, the clock-maker, the interpreter, one of the two Spanish officers, besides 12 soldiers, and 4 officers sent from Mexico, and about 50 Indians.

Lastly, according to M. de la Lande, the parallax of Venus

81;

and her distance about 35000000 leagues of 2283 toises each, on a mean of comparisons with observations made in the north of Europe, at Cajaneburg and Wardhus.

END OF THE SIXTIETH VOLUME OF THE ORIGINAL.

I. Remarks on the Nature of the Soil of Naples, and its Neighbourhood. By the Hon. Wm. Hamilton. p. 1. Vol. LXI, Anno 1771.

This paper and the following one may be consulted in the collection of Sir W. H.'s Essays, published in 8vo. 1772.

H. Extract of another Letter from Mr. Hamilton, on the same Subject. p. 48..

By

III. Observation of the Transit of Mercury over the Sun, Nov. 9, 1769. J. Winthrop, Esq., F. R. S., Cambridge, New England. p. 51. On Thursday the 9th of November, Mr. W. had an opportunity of observing the transit of Mercury. He had carefully adjusted his clock to the apparent time, by correspondent altitudes of the sun, taken with the quadrant for several days before, and with the same reflecting telescope as he used for the transit of Venus. He first perceived the little planet making an impression on the sun's limb at 2h 52m 41'; and it appeared wholly within at 53m 58 apparent time. The sun set before the planet reached the middle of its course; and for a considerable time before sun-set, it was so cloudy, that the planet could not be discerned. So that he made no observations of consequence except that of the beginning, at which time the sun was perfectly clear. This transit completes 3 periods of 46 years, since the first observation of Gassendi at Paris, in 1631. IV. Observations on the Heat of the Ground on Mount Vesuvius. By John Howard, Esq., F. R. S. p. 53.

Mr. H. here communicates some observations which he made in June, on the heat of the ground on mount Vesuvius, near Naples. On ascending the mountain, he often immerged the bulb of a thermometer in the ground, but found no sensible heat for some time; the first rising in the thermometer was 114o; every 2 or 3 minutes, he observed the instrument, till he gained the summit. At those times, he found it rising to 122°, 137°, 147° 164°, and 172o: on the top, in two places, in the interstices between the hard lava, it was 218°. Such a degree of heat, after he had overcome the inconvenience of the exhalations, raised his curiosity to know if there was a still greater degree of heat in the mouth of the mountain. Accordingly, he made a small descent, and, by 2 observations carefully and attentively made, the thermometer both times stood at 240°.

If it should be asked, how a person, either to their feet or in stooping or lying down to make the observations, could endure such a degree of heat; Mr. H. answers, that the heat, both at top and in the mouth of the mountain, was only in particular places. This was known by the fumes; the hard masses of lava were only warm, and even so tolerable as to permit him to lie on them, as he was often obliged to do, when the thermometer was immerged, to make a true observation.

V. Description of a Bird from the East Indies. By Mr. George Edwards, F. R. S. p. 55.

At Valentine House, near Ilford in Essex, the seat of Charles Raymond, Esq.; Mr. E. saw some curious birds and other animals, from the East Indies; among

these he discovered a rare bird, not before known to him.* It is of a new genus, and the only species of the genus hitherto known to him. It is about the size of a heron, see fig. 1, pl. 3;† and has a good deal of the appearance of birds of the heron and crane kind, except that the neck is a little shorter. On first sight, he thought the bird belonged to that genus; but, on a closer view,' he judged it to be no wader in the water, for though the legs be as long or longer than in herons, &c. yet they are feathered down to the knees, which we do not find in birds who wade in shallow waters, to seek their food. The toes in this bird are also much shorter than they are in herons, so that he thinks it must be placed among land birds. The bill is exactly like those of hawks, and other birds of prey, which is the only instance he has discovered in any of the long legged kind of birds; the talons or claws are small and unfit for a bird of prey, and the eyes are of a dark colour, placed in spaces covered with a bare skin of an orange colour, on each side of the head. It has a beautiful crest, composed of many long painted feathers tipped with black, hanging backward. The beak, head, neck, back, breast, and upper covert feathers of the wings, are of a bluish ash-colour, rather lighter on the breast than on the back. The belly, thighs, the greater wing-feathers, and tail, are black, the tail feathers being tipped with white; the legs and feet are of a reddish flesh-colour, the claws black. This bird was called a snake-eater, by those who brought it from India. He believes it may prey on small serpents, lizards, and other small reptiles. Another bird was brought with this, supposed to be the male of this species, which died soon after it was landed. Mr. Raymond's servant said it was something larger, and the crest longer, the head black, but that in other respects the two birds agreed.

VI. An Extract from the Register of the Parish of Holy Cross in Salop, being a Second Decade of Years, from Michaelmas 1760, to Michaelmas 1770, carefully digested in the following Table. By the Rev. William Gorfuch, Minister of that Parish, p. 57.

1761.

1762.

85281763.

20

22 21 19

13

3668 | 1765.

1766.

18 19 23 22 17 22

16

14 19 33

= 1767.

30

9

19 12

1768.

3831769.

1770.

Total.

20

17

198382.

19

201} 365.

Increase 17.

*This singular bird is the Falco serpentarius of the Gmelinian edition of the Systema Naturæ, but by Mr. Latham in his Ornithology is with more propriety referred to the genus Vultur, under the name of Vultur serpentarius.

+ This bird was described, under the name of the sagittarius from the Cape of Good Hope, by Mr. Vosmaer, keeper of the Stadtholder's museum at the Hague, in one of his publications in low