Royal Society. 1 39 



empyreumatic odour, which was stronger when there were 

 warts upon it ; but in no case was there the slightest burning 

 sensation, or even a disagreeable sensation of heat. Hence 

 certain minor operations in surgery might be performed with 

 least pain by placing the foot in a bath of red-hot iron. Lastly, 

 1 made one other experiment, the result of which might have 

 been anticipated. 



I held the finger of a leathern glove, which I had well- 

 wetted inside and had placed on a wooden rod, for nearly a 

 minute in the melted iron ; on withdrawing it, the glove was 

 not only unburnt, but had only a temperature of about 132° 

 F. (I had not a thermometer with me). Conjectures and 

 theoretical views upon these remarkable phaenomena would 

 be premature without further experiments. I hope, however, 

 soon to be able to communicate some remarks upon them. 



XX. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from vol. xxxv. p. 544.] 



Dec. 21, ri^HE Bakerian Lecture was delivered by Professor Gra- 

 1849, L ham, F.R.S., " On the Diffusion of Liquids." 

 The apparatus used in studying the diffusion of salts and other 

 substances into water was very simple. It consisted of an open 

 phial to contain the solution of the salt to be diffused, which was 

 entirely immersed in a large jar of pure water, so that the solution 

 in the phial communicated freely with the latter. Phials cast in a 

 mould of the capacity of four ounces of water, or more nearly 2000 

 grains, were generally employed, which were ground down to a uni- 

 form height of 3"8 inches. The neck was 0*5 inch in depth, and the 

 aperture or mouth of the phial 1*25 inch in diameter. The phial was 

 filled up with the solution to be diffused till it reached the point of 

 a pin dipping exactly 0*5 inch into the mouth of the bottle. This 

 being the solution cell or bottle, and the external jar the " water- 

 jar," the pair together form a " diffusion cell." The diffusion was 

 stopped, generally after seven or eight days, by closing the mouth 

 of the phial with a plate of glass, and then raising it out of the 

 water-jar. The quantity of salt which had found its way into the 

 water-jar — the diffusion product as it was called — was then deter- 

 mined by evaporating to dryness. 



The characters of liquid diffusion were first examined in detail 

 with reference to common salt. 



It was found, first, that with solutions containing 1, 2, 3 and 4 

 per cent, of salt, the quantities which diffused out of the phials into 

 the water of the jars, and were obtained by evaporating the latter, 

 in a constant period of eight days, were as nearly in proportion to 

 these numbers, as 1, 1'99, 3'01 and 4*00; and that in repetitions of 



