78 KOUUTH REPOUT — 1834. 



count of itself for the spread of contagious emanations, and is ap- 

 plicable chiefly to a quiescent condition of the atmosphere. But 

 it is known that contagious poisons may be conveyed by the mo- 

 tion of masses of air, which mechanically sweep those effluvia 

 along with them, in a state consistent with their activity at mo- 

 derate distances. Of this it is sufficient to cite the following, 

 out of several similar examples : — 1. At the Old Bailey Sessions 

 held in London in May 1750, the poisonof jail-fever was wafted 

 by a current of air from a prisoner at the bar, in such a direc- 

 tion as to infect the lord mayor, two of the judges, several of the 

 barristers, and eight of the Middlesex jury, who all died in con- 

 sequence ; but all the London jury, M'ho sat out of the current, 

 escaped*. The black assizes at Exeter and Oxford were distin- 

 guished by similar catastrophes. 2. Even in the open atmo- 

 sphere, infection may be propagated to small distances. Dr. 

 Haygarth relates an instance, the circumstances of vvhich were 

 strictly investigated, in which a child was infected with small- 

 pox, bypassing another sick of that disease on the walls of the 

 city of Chester, where they are about a yard and a half broadf. 

 3. Howard and Russell agree, that, in the open air the contagion 

 of tlie plague lurks chiefly to leeward ; and they ascribe their own 

 exemption from its effects, when examining patients out of 

 doors, to the precaution of always standing to the windward of 

 the sick. It is probable that currents of low degrees of force are 

 more dangerous vehicles of contagion than strong gales or 

 storms, since the latter must not only dilute the poisonous va- 

 pours below their point of activity, but rapidly carry them oft", 

 so diluted, to a distance. 



XXL There is no reason to believe that the atmosphere of an 

 extensive district, or even of a city or open street, can be min- 

 gled with such a proportion of animal contagion, as to become 

 infectious to numbers. The extreme mobility of the particles of 

 air among each other, and the almost unceasing variations of 

 temperature at the earth's svirface, occasion constant though 

 sometimes scarcely perceptible ciirrents, which mingle any poi- 

 sonous vapours, that may be abroad, with the general atmospheric 

 mass. All experience, indeed, as well as general reasoning, is 

 against the ivide diffusion of animal contagion in an active state. 

 The smallpox, we are assured by Dr. Haygarth, was never known 

 to spread from house to house, even in the most confined parts 

 of the city or suburbs of Chester, provided the rule of non-inter- 

 course with infected families was strictly observed %. The plague 

 does not cross the narrowest streets or alleys at Constantinople, 



• Gentleman's Magazine, 1750. f Inquiry, pp. 97 and 100. 



X Inquiry and Sketch of a Plan, Sec. 



