travellers relating that thefe countries are more infested with it than most other parts of Africa. Grand Cairo is crouded with vaft numbers of inhabitants, who for the moft part live very poorly and naftily; the streets are very narrow, and clofe: it is fituate in a fandy plain at the foot of a mountain, which by keeping off the winds, that would refresh the air, makes the heats very ftifling. Through the midit of it paffes a great canal, which is filled with water at the overflowing of the Nile; and after the river is decreafed, is gradually dried up into this the people throw all manner of filth, carrion, &c. fo that the ftench which arifes from this, and the mud together, is infufferably offenfive *. In this pofture of things, the plague every year conftantly preys upon the inhabitants; and is only ftopt, when the Nile, by overflowing, washes away this load of filth; the cold winds, which fet in at the fame time, lending their affiftance, by purifying the air. In Æthiopia, thofe prodigious fwarms of locusts, which at fome times caufe a famine, by devouring the fruits of the earth, unless they happen to be carried by the winds clear off into the fea, are obferved to entail a new mifchief upon the country, when they die and rot, by raifing a peftilence +; the putrefaction being heightened by the exceffive intemperance of the climate, which is fo very great in this country, that it is infefted with violent rains at one feafon of the year, for three or four months together . And it is par * Vid. le Brun voyage au Levant, c. xxxviii. + Vid. Ludolf. hiftor. Ethiop. lib. i. c. 13. & D. Auguft. de civitat. Dei, lib. iii. c. ult. dolf. hiftor. Æthiop. lib. i. c. 5. & comment. ‡ Vid. Lu ticularly ticularly obferved of this country, that the plague ufually invades it, whenever rains fall during the fultry heats of July and August *, that is, as Lucretius expreffes it, when the earth is Intempeftivis pluviisque et folibus iƐta †. Now, if we compare this laft remark of the intemperance of the climate in Ethiopia, with what the Arabian phyficians ‡, who lived near thefe countries, declare, that peftilences are brought by unfeafonable moistures, heats, and want of winds; I believe we fhall be fully inftructed in the ufual cause of this difcafe. Which, from all thefe obfervations compared together, I conclude to arife from the putrefaction fo conftantly generated in thefe countries, when that is heightened and increased by the ill state of air now defcribed; and especially from the putrefaction of animal fubftances. It is very plain, that animal bodies are capable of being altered into a matter fit to breed this difeafe : because this is the cafe of every one who is fick of it, the humours in him being corrupted into a substance which will infect others. And it is not improbable, that the volatile parts with which animals abound, may in fome ill states of air in the fultry heats of Africa be converted by putrefaction into a fubftance of the fame kind: fince, in thefe colder regions, we fometimes find them to contract a greater degree of acrimony than most other fubftances will do by putrefying, and alfo more dangerous for men to come within the reach of their action; as in thofe perni * J. Leo hift. Afric. lib. i. + Lib. vi. ver. 1ico. Rhaf. et. Avicen. cious, and even poifonous juices, which are fometimes. generated in corrupted carcafes: of which I have formerly given one very remarkable inftance, and, if it were neceffary, many more might be produced, efpecially in hydropic bodies, and in cancerous tumours. Nay more, we find animal putrefaction fometimes to produce in thefe northern climates very fatal distempers, though they do not arise to the malignity of the true plague: for fuch fevers are often bred, where a large number of people are closely confined together; as in gaols, fieges, and camps. And perhaps it may not be here amifs to remark, that the Egyptians of old were fo fenfible how much the putridness of dead animals contributed towards breeding the plague, that they worshipped the bird Ibis for the fervice it did in devouring great numbers of ferpents; which they obferved did hurt by their ftench when dead, as well as by their bite when alive t. : But no kind of putrefaction is ever heightened in thefe European countries to a degree capable of producing the true plague and we learn from the ob fervation of the Arabian phyficians, that fome indifpofition of the air is neceffary in the hottest climates, either to caufe fo exalted a corruption of the forementioned fubftances, or at leaft to enforce upon mens bodies the action of the effluvia exhaled from thofe fubftances, while they putrefy. Both which effects may well be expected from the fenfible ill qua* Effay on poifons. + Cicero de nat. Deor. lib. i. $36. freaking of thefe birds, fays: Avertunt peftem ab Egypto, cum volucres argues ex vaftitate Libye vento Africo invectas interficiunt atque confumunt ; ex quo fit ut illæ nec morfu vivæ noceant, nec odore mortua. lities of the air before defcribed, whenever they continue and exert their force together any confiderable time. What I have here advanced of the first original of the plague, appears to me fo reafonable, that I cannot enough wonder at authors for quitting the confideration of fuch manifeft caufes for hidden qualities; fuch as malignant influences of the heavens; arfenical, bituminous, or other mineral effluvia, with the like imaginary or uncertain agents. : This however I do not fay with defign abfolutely to exclude all diforders in the air, that are more latent than the intemperate heat and moisture before. mentioned, from a fhare in increafing and promoting the infection of the plague, where it is once bred : for I rather think this muft fometimes be the cafe; like to what is obferved among us in relation to another infectious diftemper, namely, the finall-pox, which is most commonly fpread and propagated by the fame manifeft qualities of the air as thofe here described notwithstanding which, this diftemper is sometimes known to rage with great violence in the very oppofite conftitution of air, viz. in the winter during dry and frofty weather. But to breed a diftemper, and to give force to it when bred, are two different things. And though we fhould allow any fuch fecret change in the air to affift in the first production of the difeafe; yet it may juftly be cenfured in these writers, that they should undertake to determine the fpecific nature of thefe fecret changes and alterations, which we have no means at all of difcovering: fince they do not fhew themselves in any fuch fenfible manner, as to come directly under our examination; examination; nor yet do their effects, in producing the plague, point out any thing of their specific na ture. All that we know is this, that the cause of the plague, whatever it be, is of fuch a nature, that when taken into the body, it works fuch changes in the blood and juices, as to produce this difeafe, by fuddenly giving fome parts of the humours fuch corrofive qualities, that they either excite inward inflammations and gangrenes, or push out carbuncles. and bubo's; the matter of which, when fuppurated, communicates the like difeafe to others: but of the manner how this is done, I fhall difcourfe in the following chapter. I CHA P. II. Of the causes which spread the plague. Have been thus particular in tracing the plague up to its first origin, in order to remove, as much as poffible, all objections against what I fhall fay of the causes which excite and propagate it among us. This is done by contagion. Those who are ftrangers to the full power of this, that is, those who do not understand how fubtile it is, and how widely the diftemper may be fpread by infection, afcribe the rife of it wholly to the malignant quality of the air in all places, where-ever it happens; and, on the other hand, fome have thought that the confideration of the infectious nature of the difeafe muft exclude all regard to the influence of the air: whereas the contagion accompanying the difeafe, and the dif pofition |