TIIEIK BEDEOOMS.

19

about 27 cubic feet (46,656 cubic inches) of " vital air " in tliccourse of 24 hours, and exhales, in lieu of tliis, about 24cubic feet of " mepbitic gas " in the same time. To obtain thedaily cubic yard of oxygen, a person must be supplied withabout 5 cubic yards of fresli air per diem (for tbis is theproportion in which the vital gas exists in the atmosphere),and evon this quantity should be so continually changedthroughout the day, that the carbonic acid evolved from thelungs may never reach the noxious ratio of 1 per cent of theair in which we live.

Now let us apply these facts, that have become almost plati-tudes in our own country, as tests of the sanitary condition ofeven the middle-class Rhenish sitting and sleeping-rooms.The bedroom in which we and our wife have to sleep mea-sures exactly 14 feet Square and 8 feet high, so that it containsnot quite 1600 cubic feet of air. To this there is no inlet forany fresh supply, nor outlet for the products of respiration,except through the Windows or door — tbe chimney to thestove consisting of a yard or so of narrow iron-piping tbrustinto a hole in the wall, and the 4-inch door to the cast-iron fur-nace being intended to be kept closed. Now the 1600 cubic feetof air locked up within the walls of our Chamber contain, in anordinary State, rather more than 1J cubic foot of carbonic acid ;but when, as we have said, the proportion of the latter gasrises to 16 cubic feet (1 per cent) the atmosphere becomespoisonous. Let us see, then, in what time this would takeplace. A grown person evolves, say, 1 cubic foot of mephiticgas from the lungs every hour, so that two persons wouldexhale 14 J cubic feet in little better than 7 5 hours ; and this,with the normal quantity of lj cubic foot, would raise theamount of carbonic acid to the poisonous proportion. Conse-quently, in a night of rather more than 6 hours' duration,

c 2