iii. It is composed of carbonic acid and azote, in very variable

proportions. The following experiment was frequently made. The bubbles of air which are disengaged from the skin were received into a funnel, the top of which was closed: they were then passed into a graduated tube, and agitated with a solution of potash. The height to which the solution rose in the tube indicated the quantities of carbonic acid that had been absorbed. All these operations were made at the same temperature and pressure. Neither hydrogen nor oxygen gas were discovered in this air.