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on the roofs of large houses, exposed to the morning sun: this they daily do for some time, to collect themselves before they take their flight.

Next, to confirm this opinion, that the migration of some species of swallows is certain, Mr. C. thinks he has some undoubted proofs. He has often heard Sir Charles Wager, first lord of the admiralty, relate that in one of his voyages home, in the spring of the year, as he came into soundings in our channel, a great flock of swallows came and settled on all his rigging: every rope was covered, they hung on one another like a swarm of bees; the decks and carvings were filled with them; they seemed almost spent and famished, and were only feathers and bones; but being recruited with a night's rest, they took their flight in the morning.

Capt. Wright, a very honest man, said the like happened to him in a voyage from Philadelphia hither. But a yet stronger confirmation of the swallows being birds of passage, is the observation in Mr. Adanson's history of Senegal, lately published; which is, as near as may be literally translated, from the author's own words; viz. The 6th of the same month (October) at half an hour past 6 in the evening, being about 50 leagues from the coast (between the island of Gorea and Senegal), 4 swallows came to take up their night's lodging on the ship, and alighted on the shrouds. He easily caught all 4, and knew them to be the true European swallows. This lucky incident confirmed him in the opinion he had formed, that these birds pass the seas to get into the countries of the torrid zone, at the approach of winter in Europe; and to that purpose he has since remarked, that they do not appear at Senegal but in that season. A circumstance no less worthy of note is, that at Senegal the swallows do not build nests as in Europe; but lie every night by pairs, or single, in the sand upon the sea-shore, where they rather chuse to fix their habitation than up in the country.' Hist. de Senegal, p. 67.

This observation, (as it comes from a professed naturalist, and one who went into those countries on purpose to collect what was curious in that way) seems to put the matter out of doubt; and the hearsay stories of ignorant peasants and credulous people are by no means to be put in competition with it.

Mr. C. was for many years very watchful in taking notice of the times when the swallows leave us, and had twice seen them undoubtedly taking their flight. At two different years, on the 27th and 29th of September, walking in his garden at noon, on very clear sunshiny days, and looking up into the sky, at a very great height, he distinctly saw an innumerable number of swallows, soaring round and round, higher and higher, until his eyes were so pained with looking, that he could no longer discern them.

But as Mr. Klein seems to be so positive, that the hirundo riparia, or sand

martin, at the approach of winter, retires into the holes, in which that species breed up their young, and made their summer's residence, and there pass that cold season in a dormant state, as snakes, lizards, and some other animals do, Mr. C. was the more solicitous to come at the truth. But as these sandy precipices, in which these martins build, are mostly inaccessible, some years passed before he could find a situation where the experiment could be fairly made, without difficulty or danger. Such a sand-hill he found in the parish of Byfleet in Surry. The clergyman being his friend, and well qualified to make the experiment, at his request, was so obliging to undertake it. He gives his letter in his own. words.


Byfleet, October 22, 1757.

I took a square of about 12 feet, over that part of the cliff where the holes were thickest, which in going down from the surface, I judged would take in about 40 holes. I set to work, and came to the holes; but found no martins, nothing but old nests in the farthest end of the holes, which were from a foot and half to two feet and half deep from the entrance. We carefully searched 40 holes, but found no birds; but at least 30 of them had nests. The passage to them was very near in a straight horizontal line; the nest was sunk about an inch and half below the level of the passage; the materials next the bottom were straws, then coarse and fine grasses; the whole structure of no great elegance. The few eggs that were left behind were of a clear unspotted white, the size of a robin-red-breast's.'

This fair trial, being made by a gentleman of veracity and ability, is very conclusive; for it certainly proves that the sand martins do not take up their winter abode in their summer dwellings. Therefore there is sufficient reason to believe from the before-recited observations on the common swallows, and this so recently made on the sand martins, that they are all birds of passage.

Additional Remark.-There are 4 distinct species of birds that go under the general name swallow; viz. the swift or black martin; 2, the swallow, that builds in chimneys; 3, the martin that builds against houses; 4, the sand martin, that builds in sand-banks. Mr. C. thinks he has clearly proved that some of these species are birds of passage. But some of his friends assert that they pass the winter in cliffs or caverns of the earth, in banks or precipices. What is much to be regretted is, that the gentlemen were not curious enough to distinguish the particular species which they found in a torpid state. Mr. Adanson, in his ac count of Senegal, has omitted this. So that nothing certain can yet be pronounced, which species stays, or which goes.

XLI. Observations on the Comet seen in January 1760. By James Short, M.A., F.R.S. P. 465.

A comet has made its appearance near the constellation of Eridanus, a little to the westward of Orion. Last night (Jan. 9) Mr. S. took its transit over the meridian, and likewise its declination. Its nucleus was small, subtending an angle of not more than 5 or 6 seconds, but very visible through a 2-feet reflector magnifying about 70 times. Its motion is to the westward, with a considerable velocity, seemingly about 2° in a day; for about an hour and a half after taking its transit, he judged it had advanced about 10 or 12 minutes; which was about the rate of the great comet, when it first was seen in the end of the year 1743. This comet is very visible to the naked eye, though no tail could be perceived; and therefore he concluded it was going down to the sun.

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XLII. Observations on the same Comet. By the Rev. J. Michell, M.A. p. 466. The first observations gave its distance from K Orion, is 3° 29′; from Rigel, 11° 46'; from Betelgeuse, 17° 10'; and from Sirius, 12° 56'. All these observations were made between a quarter and half an hour past 9, and in the order here set down. At 1h 22m, its distance from Rigel was 7° 6'; at 1h 24m, from Betelgeuse 15° 53′; and at 1h 36m, its distance from Sirius was 17° 36′.

XLIII An Account of the same Comet. By Nicolas Munckley, of Lincoln'sInn, Esq. p. 467.

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Jan. 9, 1760, Mr. M. observed what appeared to be evidently a comet, west of the constellation of Orion, over the two stars marked and in the river Eridanus, but nearer the latter than the former; right ascension about 66°, declination about 3° s. It was something dimmer and larger than either of these stars; and through a telescope appeared magnified, and surrounded with a broad, faint, ill defined haziness, like the last comet, such as plainly distinguished it from any thing else in the heavens.

XLIV. Of the same Comet. By Mr. Mark Day. p. 469.

Mr. D. Jan. 9, about 5 o'clock, observed the comet in the southern hemisphere, near the northern extremity of the river Eridanus, tending towards Pegasus, and thought it would cross the ecliptic about 20° in Aries. It moved one degree in less than one hour and half; but seemed too hasty to give the astronc

mers leave to make many observations on it, unless the weather proved favourable. It passed the meridian about 9.

XLV. On the Vitriolic Waters of Amlwch, in the Isle of Anglesey; with occasional Remarks on the Hartfell Spa, described in the 1st Vol. of the Edinburgh Essays and Observations, and in the 49th Vol. of the Phil. Trans., and their Comparison with other Waters of the same Class. By John Rutty, M. D. Dated Dublin, Feb. 15th, 1750. p. 470.

Amlwch is situated on Trasklwyn mountain, in the parish of Amlwch, in the Isle of Anglesey, the water of which was sent to Dr. R. by Ambrose Lewis, of Beaumorris, having been bottled May 31, 1757, and arrived in Dublin June 3. It appears by the hydrometer to be as light as distilled water, notwithstanding its strong impregnation. It is of a subacid taste, and very nauseously vitriolic; a lasting impression of that sort continuing in the throat giving suspicion of copper, of which however it exhibits no evidence, by any degree of the hue of that metal imparted to polished knives immersed in it, nor of sulphur, by discolouring silver. It retained the above-mentioned taste, on being exposed several days in an open vessel; quite otherwise than happens to our ordinary chalybeates. It curdled with soap: it also curdled equal parts of milk, exhibiting a pretty clear whey. With spirit of hartshorn, spirit of sal ammoniac, and the solution of potashes, it exhibited ochreous and green grumes, as the martial vitriol.

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Its appearances with galls, and other austeres, were very singular; for tormentil roots gave it only a dilute ink colour, soon fading; and green tea a dark dun colour, on standing. It had not blackened the corks, except perhaps one out of 6; and when the water was first poured out it struck no more than a slightly bluish tincture with galls; which tincture, on standing all night, became like a dilute ink; but in a glass exposed 32 hours, the galls struck the dilute ink colour sooner and in some of the water, which he left exposed 4 days, and in some of it, which he left in a phial corked, but only full, 3 weeks, the effect was very different; for to each portion of water so exposed, as before mentioned, the galls imparted a most beautiful bright sky-blue; which blue tincture, a little spirit of vitriol instantly destroyed.

Hence may be seen the fallacy of trusting to a few appearances, and the danger of rash conclusions, without repetitions of experiments and observations; which, if they had been omitted, he had been led to conclude this water to be but slightly impregnated with either a chalybeate or vitriolic principle; with which last it is however assuredly strongly saturated, though the ordinary test with galls does not discover it clearly by the blue tincture, until the dissolving acid is partly exhaled.

The Analysis.-It deposits an ochre, which serves for painting.-It also deposits in the bottles a sediment partly of a red and yellowish colour, and partly white and raggy which sparkled, and smelt strong, on the red hot iron.-Two pounds 11 oz. yielded 16 grs. (i. e. a gallon 49 grs.) of a light green sediment, of an acid smell, and of an highly acid, vitriolic, and nauseous taste. It ferments strongly, both with solution of potashes, and with spirit of sal ammoniac; and separates a green and ochrcous matter with the last. Galls added to its dilutum in distilled water turned it of a deep blue: the characteristic of inartial vitriol, to which it also agrees in the experiment of the last paragraph. It produced some degree of coagulation with albumen ovi; and some slight opacity, and small grumes, with saliva. It turned of a brown greenish colour with syrup of violets. It was not attracted by the magnet, until roasted in the crucible; and then it was strongly attracted, and turned as red as minium. It appears therefore that Amlwch water is strongly impregnated with an acid martial vitriol. It kills all the fish in its passage. It has sometimes been drunk, but cannot be borne in a greater dose than a pint, unless diluted with common water, being otherwise vomited up. It cures the mange in horses, and the itch in men, by bathing.

From the above account of the Amlwch water, it appears evidently to agree with that of the Hartfell, above mentioned, and described in the Edinburgh Essays, and in the Phil. Trans. even in certain distinguishing characters common to both, and in which they differ from our ordinary chalybeate waters; viz. 1. In the acid and vitriolic taste, which moreover they retain, when long kept, and at a distance from their fountains; and even on boiling, yielding an acid vitriolic salt, on exhaling to dryness, which the common chalybeates never do, but lose their strength by a small degree of heat. 2. In the blue tincture, which they give with galls; another distinguishing character of English vitriol, of which a weaker solution, like the common chalybeates, gives only the purple colour with galls. 3. In exhibiting green clouds, or grumes, with oil of tartar, like the martial vitriol.

The same, or like appearances, are exhibited by the Shadwell water; by another at Swansea in Wales; and on a late diligent search into the waters of this kingdom, by those of Kilbrew, in the county of Meath; of Ballymurtogh, in the county of Wicklow; and Cross and Coshmnore, in the county of Waterford, and some others: and to conclude, as crystals of martial vitriol have been demonstrated in several of them, Dr. R. does not hesitate to pronounce them acid vitriolic waters; which waters, as they are new in practice, and different in operation and effects from the common chalybeates, he apprehends it will be worth while to endeavour to place them in a more conspicuous point of view.

There are indeed in these waters different degrees of acrimony; for though

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