A treatise on ventilators. Wherein an account is given of the happy effects of the several trials that have been made of them, in different Ways and for different Purposes: Which has occasioned their being received with general Approbation and Applause, on account of their Utility for the great Benefit of Mankind. As also Of what farther Hints and Improvements in several other useful Ways, have occurred since the Publication of the former Treatise. Part second. By Stephen Hales, D. D. Clerk of the Closet to her Royal Highness the Princess of Wales, F. R. S. and Member of the Royal Academy of Sciences at Paris and Bolognia.