322 



the girders, directly as the amount of deflection into the depth of 

 the metal. 



The paper concludes by pointing out the important amount of 

 this resistance, the operation of which has been hitherto unknown, 

 and which in cast iron exceeds the tensile strength of the metal, and 

 shows that comparisons of the strength of different forms of section, 

 based on the existing theory, which assumes the resistance at the 

 outer fibre to be constant and equal to the tensile strength of the 

 metal, must be entirely fallacious. 



The paper is accompanied by full details of all the experiments, 

 and the measurements for determining the position of the neutral 

 axis. 



II. "On the Metallic and some other Oxides, in relation to 

 Catalytic Phenomena." By the Rev. J. EYRE ASH BY. 

 Communicated by the Rev. JOHN BARLOW, F.R.S. Re- 

 ceived March 8, 1855. 



I purpose to detail some experiments on the metallic (and a few 

 other) oxides, made with a view to ascertain their powers to produce 

 and maintain, catalytically, the combustion of various gases and va- 

 pours ; and to annex such considerations as appear to be suggested 

 by the facts. By catalysis I understand the operation of one body 

 upon another, under favourable circumstances, whereby the second 

 body is resolved into new chemical combinations, while the first 

 (whatever may happen during the process) remains finally un- 

 changed. This must be taken as not including explosion by per- 

 cussion, in which the change takes place owing to the external 

 application of dynamic force. 



The apparatus for experimenting comprehends a variety of shal- 

 low capsules ; wire-gauze, of iron, copper, and brass, of different de- 

 grees of fineness, cut into discs a little larger than the vessels on 

 which they are to be superimposed ; a spirit-lamp with large wick ; 

 a pair of pliers, and a few rings of wire to support the gauze, if 

 necessary, while heating it in the spirit flame. The method of pro- 

 cedure is simple : the watch-glass, or capsule, is nearly filled with 



