wherein condenfation of vapour is formed, by mixing the atmospheric air with that which had been rarefied, or by emitting into the atmosphere air which had been condenfed. In all those cases, there is the mixture of two portions of the atmosphere, in fufficiently different temperatures, to produce condensation of humidity, which actually happens. Thus, all those appearances are properly explained by the theory, or, as experiments, they confirm the affumed propofition.

BUT if thus every particular example is a proof, and if each example is unexceptionable in its kind, what degree of evidence must arise from the united teftimony of every poffible experiment almost which can be adduced in relation to the fubject? It is to be prefumed that M. DE LUC, with all his extenfive knowledge of nature, could not adduce one fhadow of a fact by which the alleged propofition could be called in question or difproved.

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M. DE LUC concludes in the following manner, (parag. 588.) Je ne vois donc rien dans ces faits, qui contribue à éclaircir "la queftion de la pluie; et par conséquent elle me paroît "refter au point ou je l'avois amené avant que d'entrer dans ce nouvel examen. Je tire même du memoire du Dr HUTTON, ces deux confequences, qui justifient le travail que j'ai "enterpris. Quoiqu'il paroiffe s'être beaucoup occupé des

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phénomènes de la pluie, aucune théorie à leur egard ne l'avoit "fatisfait ; et d'après ce qui lui etoit connu des loix de l'hygrologie, il avoit conclu, que la précipitation de l'eau fimplement evaporée, ne pouvoit être produite que par refroidiffement. Or, ce font, entre autres, ces deux motifs qui m'ont "conduit dans mes recherches."

M. DE LUC had no occafion to justify his undertaking by any opinions of mine. His writings will always contain matter fufficient to interest the public; and his ideas of hygrology must be supported upon their own bottom. I therefore wish he had not given as my ideas expreffions which, however,

in fome respects, fufficiently just, may bear perhaps another interpretation. That the precipitation of water fimply evaporated cannot be produced except by cooling, is an expreffion which, though not contrary to my idea, does not contain precifely my opinion. Water is not precipitated from the atmosphere in time of rain by the cooling of the air, in the ordinary fense of that expreffion, that is, by the abstraction of a certain quantity of its heat, which is then communicated to fome other body; but it is because the air is not able to contain fo great a quantity of water, in proportion to its heat, when it is in a lower temperature. The The compound mafs of air, which in the formation of rain precipitates water, is not cooled, fo far as I know, below the mean temperature of the different maffes of unequally heated air which have concurred to form it; but this mean temperature does not fuffice to evaporate all the water which had been contained in these maffes feparately. This, however, is only by the by; and I now proceed to the material part of his conclufion, where he thus continues:

QUANT à l'hypothèse que je viens d'examiner, elle étoit "très naturelle dans l'état des faits connus; puifqu'il n'étoit pas poffible de concevoir d'aucune autre manière, que des "mêlanges d'airs à differentes temperatures, puffent produire "des pluies abondantes: et la vraisemblance de cette hypothèse ne pouvoit être détruite, que par un genre d'experiences et "d'obfervations, qui ne fait que de naître en physique avec l'hygromètre."

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IN answer to this, I have but to obferve, that, had M. de Luc contented himself with saying, as he here has done, that the probability of this hypothefis could not be overturned, but by a fort of phyfical experiments and obfervations which have just taken their birth with the hygrometer, I should have waited patiently until those experiments and observations had arrived at that maturity which might enable them to confute my theory. But M. DE LUC has undertaken to confute it upon VOL. II.

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other

other principles, which do not require any profound knowledge of that instrument. It is only to these that I have answered; and I beg it to be understood, that the theory which I have endeavoured to establish, is just now as open to the experiments of the hygrometer, whether for being fupported by them or overthrown, as if nothing had been written upon the fubject.

IX.

IX. An ACCOUNT of a DISTEMPER, by the common People in England vulgarly called the MUMP S. By ROBERT HAMILTON, M. D. Fellow of the Royal College of Phyficians, F. R. S. EDIN. and Physician at Lynn Regis, in Norfolk *.

TH

HE mumps, or what I beg leave to call angina maxillaris, is an epidemic disease of a very fingular nature. It has appeared fometimes to be pretty general; but this has not been the cafe for many years in this place. It seems to be analogous to, if not the fame diftemper with that called the branks, by the common people in Scotland. In the general account of epidemics, in the first volume of the Medical Effays of Edinburgh, a diforder is mentioned which feems to have been a flight degree of that which is the fubject of the following paper. I have had much practice in this disease, and indeed was once reduced to the utmost danger by it myself.

IN the following paper, I fhall not pretend to give a fyftematic treatise on the mumps. I fhall relate what was the result of obfervation, both in regard to the history and cure of this difease; and as I fhall faithfully detail what I actually faw, I flatter myself, that this account will not be unworthy of the perufal of future observers.

This paper was read before the Philofophical Society of Edinburgh, Auguft 5. 1773It is now printed by order of the Committee for publication of the Transactions of the Royal Society of Edinburgh.

THE hiftory of the mumps is as follows:

A LASSITUDE, a heavinefs, a general restlefs uneafinefs, not easily described, are perceived several days before the fwelling which characterifes the difeafe, begins to appear. Thefe difagreeable feelings are attended with gentle rigors, and some degree of fever, which, being flight, is commonly difregarded. Then a stiffness, with obtufe pain, is felt in one or both fides of the articulation of the lower jaw, impeding its motion and of course mastication; which fymptoms increafing, a fwelling appears upon the parts the following day, and quickly extends to the parotid glands, the neighbouring skin, and cellular membrane. Here, in fome, it stops without difcolouring the skin; and, by keeping the parts moderately warm, and cautiously avoiding the cold external air, the patient is foon freed from it, without any medical affiftance. But, when this is not the cafe, the parts affected generally redden the next day, the tumor becomes more diffused, and sometimes increases so suddenly in fize, that, on the third day from its first appearance, it occupies the falivary glands and furrounding cellular membrane on that fide. and, if both sides are affected, the parts are so much fwelled, and the tumor defcends fo low, that the countenance is rendered of a frightful enormous magnitude; and now deglutition becomes more or lefs impeded. All this is frequently without much pain; but most commonly there is now a great deal, and a confiderable degree of fever. When this happens, the countenance appears florid, and a dusky erysipelatous inflammation covers the tumor, which is deepest in colour where there is the greatest hardness, viz. on the parotid and maxillary glands. In many subjects here it ends. And it seems probable from the natural refolution of the disease, which now immediately follows, that the tumor has attained its greatest mag

nitude,