depend on the very nicest tone of the fibres. And if these are in the smallest degree relaxed, or their elasticity diminished, how is it possible that their contractions and expansions can so readily obey the will, as to produce these effects The opening of the glottis which forms the voice is extremely small, and, in every variety of tone, its diameter must suffer a sensible change; for the same diameter must ever produce the sametone.-So wonderfully minute are its contractions and dilatations, that Dr. Keil, I think, computes, that, in some voices, its opening, not more than the tenth of an inch, is divided into upwards of 1200 parts, the different sound of every one of which is perceptible to an exact ear. Now, what a nice tension of fibres must this require !. I should imagine every the most minute change in the air must cause a sen ible difference, and that in our foggy climate the fibres would be in danger of losing this wonderful sensibility; or at least that they would very often be put out of tune. It is not the same case with an ordinary voice, where the variety of divisions run through, and the volubility with which they are executed, bear no proportion to those of Gabrieli." Thus far Mr. Brydone.

He

Mr. Wraxall saw this wonderful singer at the court of Petersburgh, in the month of July, 1774. was introduced to her by Count Ruewzsky, a Polish nobleman. "She rose up, says Mr. Wraxall, with great politeness on the Count's introducing me to her, as an English gentleman who was lately arrived; and I did not lose the opportunity to enter into a conversation with her. She was perfectly free and unreserved in her replies to a num

ber of little questions which I put to her. She said, that though used to the warmer climates of Italy and Sicily, her constitution was not im paired or injured by the severity of that here; that the Empress was a bounteous mistress, and she had no reason to be dissatisfied with her present situation; but that, notwithstanding, she had a passionate desire to visit England, a journey she had been many times on the point of executing, but had never yet accomplished. I assured her how happy the English nation would be to see among them a woman of such pre-eminent merit, and how generous their patronage was to all the performers in the fine arts. I mentioned Mademoiselle Heinel to her, as a proof of the justice of my assertion; and told her, that the name of La belle Gabrieli was already too well known among us, not to insure her the most welcome reception.. I seized this moment to ask her, if she had never heard of or known a Mr. Brydone, who was at Palermo a very few years since, and had given us a description of her person and voice, as far as they admitted of it? She said she had not the pleasure to know him, nor recollected to have heard his name; but mentioned Sir William Hamilton and Lord Cowper, as persons with whom she was well acquainted, Our conversation was most agreeably interrupted by her standing up to sing. I must own, I never heard any voice so perfectly sweet, melting, and absolute in its command over the soul; nor cant any thing exceed the negligent carelessness apparent in her whole manner, while employed in this occupation, as if she despised the appearance of exertion, or any labour to please. I

am

am assured, however, her powers are somewhat impaired since her arrival here, and that she does not possess that compass or extent at present, which she had two years ago. The character of caprice, which she maintained in the southern parts of Europe, she has not lost here, as they universally ascribe this quality to her in the highest degree. She was at Milan, when the Empress engaged her to sing in her court. The price she demanded was 7000 rubles (or about 15001. sterling) a year, besides a house and carriage; nor would she relax the least article of the sum. They remonstrated with her on the unreasonableness of so enormous a salary, and, to induce her to diminish it, informed her, that a field-marshal,

had no more. "If that be the case, (said she) I would advise her Majesty to make one of her marshals sing." Her person, strictly considered in itself, is by no means irresistible; she does not exceed, if she reaches, the middle size; her features are small, and her eyes blue; but her neck is exquisitely white; and, as her dress usually discloses more than can strictly be confined to that part of the human body, it cannot be gazed on with impunity. Her attractions have not failed to procure her many admirers during her stay here, and she has had her favourite Muscovite, as well as her Sicilian lover. Though her salary is so ample, it is only on pe. culiar occasions and great festivals that she usually sings."

The supposed Effect of boiling upon Water, in disposing it to freeze more readily, ascertained by Experiments, by Joseph Black, M.D. Professor of Chemistry at Edinburgh, in a Letter to Sir John Pringle, Bart. P. R. S.

From the Philosophical Transactions.

To Sir John Pringle Bart. P. R. S.

Dear Sir,

WE

Edinburgh, Feb. 11, 1775. E had lately one day of a calm and clear frost; and I immediately seized the opportunity, which I missed before, to make some experiments relating to the freezing of boiled water, in comparison with that of water not boiled. I ordered some water to be boiled in the teakettle four hours. I then filled with it a Florentine flask, and im mediately applied snow to the flask until I cooled it to 48° of FAHRENHEIT, the temperature of some unboiled water, which stood in my study in a bottle; then putting four ounces of boiled, and four of the unboiled water, separately, into two equal tea-cups, I exposed them on the outside of a north window, where a thermometer pointed to 29°. The consequence was, that ice appeared first upon the boiled water; and this, in several repetitions of the experiment, with the

same boiled water, some of which were made nine hours after it was poured out of the tea-kettle. The length of time which intervened between the first appearance of ice upon the two waters was different in the different experiments. One cause of this variety was plainly a variation of the temperature of the air, which became colder in the afternoon, and made the thermometer descend gradually to 25°. Another cause was the disturbance of the water; when the unboiled water was disturbed now and then by stirring it gently with a quill toothpick, the ice was formed upon it as soon, or very nearly as soon, as upon the other; and, from what I saw, I have reason to think, that were it to be stirred incessantly, provided at the same time the experi nient were made with quantities of water, not much larger or deeper than these, it would begin to freeze full as soon. In one, of these trials, having inspected my tea-cups when they had been an hour exposed, and finding ice upon the boiled-water, and none upon the other, I gently stirred the unboiled water with my tooth-pick, and saw immediately, under my eye, fine feathers of ice formed upon its surface, which quickly increased in size and number, until there was as much ice in this cup as in the other, and all of

it formed in one minute of time, or two at most. And in the rest of the trials, though the congelation began in general later in the unboiled water than in the other; when it did begin in the former, the ice quickly increased so as, in a very short time, to equal, or nearly equal in quantity, that which had been formed more gradually in the boiled water. The opinion, therefore, which I have formed from what I have hitherto seen is, that the boiled and common water differ from one another in this respect; that whereas the common water when exposed in a state of tranquillity to air that is a few degrees colder than the freezing point, may easily be cooled to the degree of such air, and still continue perfectly fluid, provided it still remain undisturbed: the boiled water, on the contrary, cannot be preserved fluid in these circumstances; but when cooled down to the freezing point, if we attempt to make it in the least colder, a part of it is immediately changed into ice; after which, by the continued action of the cold air upon it, more ice is formed in it every moment, until the whole of it be gradually congealed before it can become as cold as the air that surrounds it. From this discovery it is easy to understand, why they find it necessary to boil the water in India, in order to obtain ice. The utnost intensity of the cold which they can obtain by all the means they employ, is probably not greater than 31° or 30° of Fahrenheit's thermometer. Common water, left undisturbed, will easily descend to

this degree without freezing; and, if they have not the means of making it colder, may continue fluid for any time, provided it be not disturbed: the refrigerating causes of that part of the world when they have done so much, have done their utmost, and can act no further upon the water. But this cannot happen to the boiled water; when the refrigerating causes have cooled it to 32°, the next effect they produce is to occasion in it the begin ning of congelation; while the water is afterwards gradually assuming the form of ice, we know, by experience, that the temperature of it must remain at 32°; it cannot be made colder, so long as any considerable part of it remains frozen. The refrigerating causes continue, therefore, to have power over it, and to act upon it, and will gradually change the whole into ice, if their action be continued sufficiently long.

un

The next object of investigation may be the cause of this difference between the boiled and the com

nion

water. In considering this point, the following idea was suggested: as we know from experience, that, by disturbing common water, we hasten the beginning of its congelation, or render it incapable of being cooled below 32o, without being congealed; may not the only difference between it and boiling water, when they are exposed together to a calm frosty air, consist in this circumstance: that the boiled water is necessarily subjected to the action of a disturbing cause, during the whole time of its

exposure, which the other is not? One effect of boiling water long, is to expel the air which it naturally contains; as soon as it cools, it begins to attract and absorb air again, until it hath recovered its former quantity; but this probably requires a considerable time. During the whole of this time, the air entering into it must occasion an agitation or disturbance in the water, which, though not sensible to the eye, may be very effectual in preventing it to become, in the least, colder than the freezing point, without beginning to freeze, in consequence of which its congelation must begin immediately after it is cooled to that point. When I reflect upon this idea, I remember a fact which appears to me to support it strongly. Fahrenheit was the first person who discovered that water, when preserved in tranquillity, may be cooled some degrees below the freezing point without freezing. He made the discovery while he was endeavouring to obtain ice from water that had been purged of its air: with this intention he had put some water into little glass globes, and having purged it of air, by boiling and the airpump, he suddenly sealed up the globes, and then exposed them to the frosty air. He was surprized to find the water remain unfrozen much longer than he expected,

meter to the water, or otherwise examine what state it was in. The immediate consequence of the admission of the air was a sudden congelation which happened in the water; and in the rest of his globes a similar production of ice was occasioned by shaking them. The inference that may be drawn from these experiments of Fahrenheit's is sufficiently obvious; it appears to me to remove all doubt with regard to the above supposition. Before these experiments of Fahrenheit occurred to my memory, I had planned a few, suggested by the above supposition, that might have led to the same conclusion; but the short duration of the frost, for one day only, did not give me time to put them in execution.

Of the stilling of Waves by means of Oil. Extracted from sundry Letters between Benjamin Franklin, LL.D FR. S. William Brown rigg, M. D. F. R. S, and the Rev. Mr. Farish*.

From the Philosophical Transactions.

Extract of a Letter from Doctor Brownrigg, to Dr. Franklin, dated Ormathwait, January 27, 1779.

friend, a worthy clergyman

and