6l2 PHILOSOPHICAL TRANSACTIONS. [anNO I67I. 



Esteeming hence, that sulphureous spirits may be fixed in earth as their ma- 

 trix, he says, that he employed the same method with all minerals, sulphurs, 

 and mercury itself, and accordingly melted various minerals with various earths 

 and clays; whereby he discovered many truths and transmutations. 



III. De Absynthio Analecta, per Joh. Michael Fehr, M. D. Lipsiae, 1668, 

 in 8vo. 



A vast deal too much about wormwood. 



Crocologia. Auth. Joh. Ferdinando Hertodt, M. D. Jenae, 1671, in Svo. 



In like manner a vast deal too much about saffron. 



IV. DeLaudano Opiato, Auth. Matth. Tillingio, M. D. Francofurti, 1671, 

 in Svo. 



A treatise on opium, superseded by the writings of modern pharmacologists. 



A Supplement to what was published N'' 73, on the Compression of 

 Air under Water. N" 75, p. 2239. 



At the desire of a particular friend, the scheme in fig. 3, pi. 14, was drawn, 

 and is now permitted to be made public at the request of another, by way of 

 supplement to what was said in the Philosophical Transactions, N° 73, of the 

 compression of air under water, in which figure, ED is made to represent the 

 tube =x; AB the distance of the upper part of the tube from the surface of 

 the water, above or under it, =b; FC the depth of the water from its surface 

 to the bottom of the air within the tube, = a; BC that part of it which re- 

 mains filled with air within the water; CD the rest thereof which is full of 

 water. 



Then, any two of the first three cc, h, and «, being given, the other is known, 

 and consequently the rest also. For, if by the incumbent weight of 33 feet 

 depth in water, the air in the tube is compressed into half the space it filled be- 

 fore; then the said 33 feet depth of water equals the weight or pressure of the 

 incumbent air on the surface of the water. 



Now as the weight or pressure of the air on the surface of the water, is to 

 the depth of the water from the surface thereof to the bottom of the air within 

 the tube, so is the length of the tube filled with air, to the length thereof filled 

 with water; that is, according to the said experiments, putting z for 33, or what- 

 ever at other times or places shall be found to be the weight or pressure of the 

 incumbent air on the surface of the w^ater, for it is not always the same ex- 

 actly ; 



