ly been brought up by hand, the confequence of which I have already ftated from feveral experiments. The foft-billed birds alfo cannot be well brought over, as the fuccedaneum for infects (their common food) is fresh meat, and particularly the hearts of animals.

I have happened, however, to hear the American mocking-bird in great perfection at Meff. Vogle's and Scott's, in Love-lane, Eaftcheap.

This bird is believed to be ftill living, and hath been in England thefe fix years. During the space of a minute, he imitated the wood lark, chaffinch, blackbird, thrufh, and fparrow. I was told alfo, that he would bark like a dog; fo that the bird feems to have no choice in his imitations, though his pipe comes nearest to our nightingale of any bird I have yet met with.

With regard to the original notes, however, of this bird, we are ftill at a lofs; as this can only be known by those who are accurately acquainted with the fong of the other American birds.

Kalm indeed informs us, that the natural fong is excellent*; but this traveller feems not to have been long enough in America to have diftinguished what were the genuine notes with us, mimics do not often fucceed but in imitations.

I have little doubt, however, but that this bird would be fully equal to the fong of the nightingale in its whole compafs; but then, from the attention which the mocker pays to any other fort of difagreeable noifes, thefe capital notes would be always debafed by a bad mixture.

We have one mocking bird in England, which is the kylark; as, contrary to a general obfervation I have before made, this bird will catch the note of any other which hangs near it; even after the skylark note is fixed. For this reafon the bird-fanciers often place the skylark next one which hath not been long caught, in order, as they term it, to keep the caged skylark honeft.

The queftion, indeed, may be afked, why the wild fkylark, with thefe powers of imitation, ever adheres to the parental note; but it must be recollected, that a bird, when at liberty, is for ever fhifting its place, and, confequently, does not hear the fame notes eternally repeated, as when it hangs in a cage near another. In a wild state, there. fore, the skylark adheres to the parental notes; as the parent cock attends the young ones, and is heard by them for fo confiderable a time.

I am aware also, that it may be afked, how birds originally came by the notes which are peculiar to each fpecies. My anfwer, however, to this is, that the origin of the notes of birds, together with its gradual progrefs, is as difficult to be traced, as that of the different languages in nations.

The lofs of the parent-cock, at the critical time for inftruction, hath undoubtedly produced those rarities, which I have before obferved are in the fong of each fpecies; because then the neftling hath either attended to the fong of some other birds; or, perhaps, invented fome new notes of its own, which are afterwards perpetuated from generation to generation, till fimilar

accidents produce other alterations. The organs of fome birds also are probably fo defective, that they cannot imitate properly the parental note, as fome men can never articalate as they fhould do. Such defects in the parent-bird must again occafion varieties, becaufe thefe defects will be continued to their defcendants, who (as I before have proved) will only attend to the parental fong. Some of thefe defcendants alfo may have imperfect organs; which will again multiply varieties in the song.

The truth is, as I before obferv. ed, that scarcely any two birds of the fame fpecies have exactly the fame notes, if they are accurately attended to, though there is a general resemblance.

Thus most people fee no difference between one fheep and another, when a large flock is before them. The fhepherd, however, knows each of them, and can fwear to them if they are loft; as can the Lincoln fhire gofherd to each goofe.

my own obfervations, is ill found. ed, and, from the nature of it, must be dangerous. I mean his maintaining, that there is nothing to be apprehended from the neighbourhood of putrid marshes.

I was particularly furprized to meet with fuch an opinion as this in a book infcribed to yourself, who have fo clearly explained the great mifchief of fuch a fituation in your excellent treatife on the difeafes of the army. On this account, I have thought it not improper to address to you the following obfervations aad experiments, which I think clearly demonstrate the fallacy of Dr. Alexander's reafoning, indifputably establish your doctrine, and, indeed, juftify the apprehenfions of all mankind in this cafe.

I think it probable enough, that putrid matter, as Dr. Alexander has endeavoured to prove, will preferve other fubftances from putrefaction; becaufe, being already faturated with the putrid effluvium, they cannot readily take any more; but Dr. Alexander was not aware, that air, thus loaded with putrid effluvium, is exceedingly noxious when taken into the lungs. I have. lately, however, had an opportunity of fully afcertaining how very noxious fuch air is.

Happening to use, at Calne, a much larger trough of water, for the purpose of my experiment, than I had done at Leeds, and not having fresh water fo near at hand as I had there, I neglected to change it, till it turned black, and became offenfive, but by no means to fuch a degree, as to deter me from making ufe of it. In this ftate of the water, I observed bubbles of air to rile from it, and efpecially in one

place,

place, to which fome shelves, that I had in it, directed them; and having fet an inverted glass veffel to catch them, in a few days I collected a confiderable quantity of this air, which iffued fpontaneously from the putrid water, and, putting nitrous air to it, I found that no change of colour or diminution enfued, fo that it must have been in the highest degree noxious. I repeated the fame experiment feveral times afterwards, and always with the fame refult.

After this, I had the curiofity to try how wholesome air would be affected by agitation in this water; when, to my real surprise, I found, that, after one minute only, a candle would not burn in it; and, after three or four minutes, it was in the fame state with the air which had iffued fpontaneously from the fame water.

I alfo found, that common air, confined in a glafs veffel, in contact only with this water, and without any agitation, would not admit a candle to burn in it after two days.

These facts certainly demonftrate, that air which either arifes from stagnant or putrid water, or which has been for fome time in contact with it, must be very unfit for refpiration; and yet Dr. Alexander's opinion is rendered fo plaufible by his experiments, that it is very pof fible that many perfons may be rendered fecure, and thoughtlefs of danger, in a fituation in which they must neceffarily breathe it. On this account, I have thought it right to make this communication as early as I conveniently could; and, as Dr. Alexander appears to be an ingenuous and benevolent man,

I doubt not but he will thank me for it.

That air issuing from water, or rather from the foft earth, or mud, at the bottom of pits containing water, is not always unwholesome, I have also had an opportunity of afcertaining. Taking a walk, about two years ago, in the neigh'bourhood of Wakefield, in Yorkfhire, I obferved bubbles of air to arife, in remarkably great plenty, from a fmall pool of water, which, upon enquiry, I was informed had been the place where fome perfons had been boring the ground in order to find coal. Thefe bubbles of air having excited my curiofity, I prefently returned, with a bafon, and other veffels proper for my purpose, and having ftirred the mud with a long ftick, I foon got about a pint of this air; and, examining it, found it to be good common air; at least a candle burned in it very well. I had not then difcovered the method of ascertaining the goodness of common air by a mixture of nitrous air. Previous to the trial, I had fuspected that this air would have been found to be inflammable.

I fhall conclude this letter with obferving, that I have found a remarkable difference in different kinds of water, with refpect to their effect on common air agitated in them, and which I am not yet able to account for. If I agitate common air in the water of a deep well, near my houfe in Calne, which is hard, but clear and sweet, a candle will not burn in it after three minutes. The fame is the cafe with the rain-water, which I get from the roof of my house. But in diftilled water, or the wa

ter

ter of a fpring-well near the house, I must agitate the air about twenty minutes before it will be fo much injured. It may be worth while to make farther experiments with respect to this property of water.

In confequence of using the rain water, and the well water abovementioned, I was very near concluding, contrary to what I have afferted in my printed papers, that common air fuffers a decompofition by great rarefaction. For when I had collected a confiderable quantity of air, which had been rarefied about four hundred times by an excellent pump made for me by Mr. Smeaton, I always found, that when I filled my receivers with the water above-mentioned, though I did it fo gradually as to occafion as little agitation as poffible, a candle would not burn in the air that remained in them. But when I used diftilled water, or fresh spring water, I undeceived myself.

tions. This parish is a part of the district of Vaud, belonging to the canton of Bern in Switzerland; and contains 169 families, and 696 inhabitants. Mr. Muret's table of the rate of mortality in it, is formed from a register of the ages at which all died in it for fifteen years. With this table he has also given tables from like registers, of the rates of mortality in feven fmall towns; in 36 country parishes and villages; in 16 parishes fituated in the Alps; in 12 corn parishes, and in 18 vintage parishes. From comparing these tables, it appears, that the probabilities of life are highest in the most hilly parts of the province, and loweft in the marshy parish juft mentioned. The difference is indeed remarkable, as will appear from the following particu lars.

One half, of all born in the mountains, live to the age of 47. In the marshy parish, one half live only to the age of 25. In the hills, one in 20, of all that are born, live to 80. In the marshy parish only one in 52 reaches this age.

In the hills, a person aged 40 has a chance, of 80 to 1, for liv

ing a year. In the marshy parith, his chance for living a year is not 30 to 1.In the hills, perfons aged 20, 30, and 40, have an even chance for living 41, 33, and 25 years respectively. In the fenny parish, perfons, at these ages, have an even chance of living only 30, 23, and 15 years.In fhort, it appears, that, though the probabili ties of life in all this country, except this one parish, are much higher than in London; yet here, after 30, they are much lower. Before the age of 30, they are indeed, higher in this parish; the reafon of which must be, that the London

air

air and cuftoms are particularly noxious to children.

I am fenfible, that obfervations, for only 15 years, in one fmall parish, do not afford as decifive and ample an authority, in the prefent cafe, as there is reason to wish for; and that, therefore, the perfect exactnefs of the particulars I have recited cannot be depended on. -They are, however, fufficiently near the truth to demonftrate, in general, the unhealthfulness of a marshy fituation; and as the regifter from whence they are derived is the only one, in fuch a fituation, which I have ever met with, and Dr. Alexander's experiments may lead fome to very wrong conclufions on this fubject, I could not help thinking that there would be no impropriety in fending you the account I have now given. If you think it of any importance, I fhall be obliged to you for reading it to the Royal Society.

I cannot help taking this opportunity to add my wifhes, that fuch regifters of mortality, as those published by Mr. Muret, were eftablished in every part of this kingdom. We might then determine immediately every fuch question as that which has occafioned this letter; and know certainly, what influence different airs, and different fituations, have on the duration of life. Two ingenious phyficians, Dr. Percival at Manchester, and Dr. Haygarth at Chefter, have lately, with much zeal, promoted inftitutions of this kind; and a great deal of ufeful information may be expected from the accurate and com

The Cafe of a Patient voiding Stones through a fiftulous Sare in the Loins, without any concomitant Discharge of Urine by the fame Paffuge: In a Letter to Dr. Maty, from Mr. S. F. Simmons.

[Read, Dec. 23, 1774-] Have taken the liberty of ad

caufe from your fituation as fecretary to the Royal Society, and the reputation you have acquired in the literary world, I have no doubt of your being very ready to receive it favourably. If you think it fuffi. ciently interefting, you will be pleased to communicate it to the Royal Society; but if you think that it has neither enough of novelty, or utility, to merit a place in their Tranfactions, I beg the favour of you to let it reft with you.

Eleanor Pilcher, the fubject of it, is about 52 years of age, and lives at Littlebourn in Kent. About 25 years ago fhe first began to complain of pain in her back, of a difficulty in making water, and of other nephritic fymptoms, which gradually increased. Soon after this he began to void gravel with her