Note 50 — CHAP. I. AIR.

At the time I am writing this, (March 8th, 1785) there has occurred a fact which proves the effect of time in generating infection. There now prevails a contagious fever in several of the hospitals in London, and, among others, in that to which I am physician. In another hospital it has been so violent, that there has been a vulgar report that the plague had broke out in it. The same fever also prevails among the poor at their own houses. The cause of it seems to be, that the cold weather has been uncommonly long and severe; for the frost began early in December, and the cold has hitherto been more like that of winter than spring. The thermometer all this month has varied from 30° to 35°. Cold is favourable to infection, by preventing ventilation; for people exclude the air in order to keep themselves warm, and the poor in particular do so on account of their bad clothing, and their not being able to afford fuel to make good fires. Heat is the great destroyer of infection, and seems to act by evaporating, and thereby dissipating it; and the effect of fires in apartments is to produce a constant change of air, thereby preventing its stagnation and corruption, and the accumulation of unwholesome effluvia. With this view, a chimney is of great use, even though no fire should be kept in it, as it serves for a ventilator. But if an aperture were to be made in an apartment merely with a view to ventilation, it should be placed in that part of the wall next the ceiling; for foul air naturally tends upwards, and the external air entering at the top of a room, would not be so apt to subject those within to the effect of cold, as it would not blow directly upon them. There would also be this advantage in jails, that apertures in this situation would not be so liable to be forced for the purpose of escape as if they were nearer the floor; and in hospitals they would be out of reach of those who, wishing to indulge in warmth, at the expence of pure air, might be induced to shut the windows. But an external communication with the air any where is of the utmost importance; and it is observable in Mr. Howard’s account of prisons, that the jail distemper was most frequently to be met with where there was no chimney.