220 Proceedings of Philosophical Societies. [March, 



at the level of the sea, is equal to 39*1386 inches of Sir George 

 Shuckburgh's scale, the scale being at 62°, and the latitude of 

 the place of observation, 51° 31' 8-3". 



An appendix to Capt. Kater's paper on the pendulum was also 

 read, containing a demonstration, by Dr. Young, of a theorem 

 discovered by M. Laplace, that if a compound pendulum be made 

 to vibrate on cylinders instead of knife edges, the distance 

 between the surfaces of the cylinders (the vibrations on each 

 being equal) will be the length of the equivalent pendulum. 



This was followed by a paper, by the same author, " On the 

 Length of the French Metre estimated in Parts of the English 

 Standard ; " from which it appears, that the length of the metre 

 in parts of Sir George Shuckburgh's standard scale, is equal to 

 39*37079 inches, each standard being brought to its proper 

 temperature. 



A paper by Mr. Knight was also read, on the heart wood of 

 trees ; the principal object of which was to show, that this portion 

 of the plant bears a more active part in the vegetable eco- 

 nomy than is usually assigned to it. The heart wood has been 

 supposed to be chiefly useful as a mechanical support to the 

 other parts, and as retaining only an inconsiderable share of 

 vitality ; whereas Mr. Knight endeavours to prove, by a series 

 of experiments, that it serves as a reservoir for the sap, or other 

 juices of the plant, during their torpid state, whence it is again 

 expelled, and sent to the bark at the renewal of vegetation in 

 the spring. 



Feb. 12. — A paper, by Sir H. Davy, was read, on the subject 

 of the experiments that have been lately performed at Edinburgh 

 by Dr. Ure, on the nature of chlorine.* The object of these 

 experiments was to prove, that water forms an essential part of 

 muriatic acid gas, by passing the gas through tubes containing 

 portions of iron or other metals, from which process water was 

 procured, and the metal was converted into a muriate. Sir H. 

 Davy, however, brings forward experiments to show, that the 

 water obtained under these circumstances was an accidental pro- 

 duct, generated by the hydrogen of the muriatic acid gas meeting 

 with oxygen, which was derived from sources not suspected by 

 Dr. Ure. When tubes of flint glass were employed for the trans- 

 mission of the gas, the oxide of lead and the alkali in the glass 

 furnished the oxygen ; and a portion of it was also furnished by 

 the atmospheric air remaining in the tube. The quantity of 

 water was always found to be diminished in proportion to the 

 care that had been taken to remove all these sources of oxygen. 



A paper, by Dr. Marshall Hall, was also read, on the action of 

 water and oxygen on iron. The author endeavours to prove, by 

 experiment, that pure water below the temperature of 212°, has 

 no action upon pure iron ; but that if the water contain any 



• Annals for Feb. p. 146, et seq. 



