372 Mr Cobbett, On the Heat generated by 



On the Heat generated by certain Fibrous Substances when 

 wetted. By Louis Cobbett, M.D., F.R.C.S. Eng. 

 [Read 21 May 1900.] 



It is well known that many fibrous materials readily absorb 

 water, but it is not so well recognised that the process is attended 

 by an evolution of heat. Dr R. E. Dudgeon 1 was I believe the 

 first to point out that if the bulb of a clinical thermometer were 

 surrounded by a little cotton-wool or a few turns of a silk hand- 

 kerchief and placed in the mouth, and the expired air breathed 

 through the wrappings, a temperature might be registered con- 

 siderably higher than that of the walls of the mouth. From this 

 he concluded — no doubt wrongly — that the temperature of the 

 breath considerably exceeds that of the mouth. Sir W. Roberts 2 

 confirmed the observation, but contested the conclusion of Dr 

 Dudgeon and attributed the rise of temperature above that of the 

 mouth to " conversion of latent heat into sensible heat, by the 

 rapid condensation of aqueous vapour," and he showed that the 

 rise of temperature was much greater when the material used to 

 surround the thermometer was previously dried, and became less 

 and less each time the observation was repeated with the same 

 strip of flannel, until on the third occasion the thermometer 

 reached 98-6° F. only. 



Dr H. F. Parsons 3 repeated Dr Dudgeon's observation with 

 the clinical thermometer, and showed that the same phenomenon 

 takes place at a higher temperature by means of the following 

 experiment. A few rolls of flannel enclosing a thermometer bulb 

 were dried in hot air at 220° F. for some time, and then allowed to 

 cool a little. As the mercury fell the index was shaken down 

 until it stood at 212° F. The roll of flannel and thermometer was 

 then placed in a tin cylinder and exposed for five minutes to 

 steam at 212° F. At the end of this time the temperature within 

 the roll was found to be 239° F. Experiments somewhat similar 

 to this have been made by Prof. Max Rubner of Berlin 4 , who has 

 found the temperature in the interior of a mass of wool dried 

 and warmed, and placed in a current of saturated steam at 100° C, 

 rise to 146° C. in ten minutes, and remain above 140° C. for over 

 an hour. 



The observations with the clinical thermometer are easily 



1 Nature, 1880, Vol. xxn. p. 241, and Vol. xxni. p. 10. 



2 Ibid. Vol. xxni. p. 55. 



3 Supplement to the Fourteenth Annual Local Government Report, 1884. 



4 Hygienische Rundschau, Berlin, 1898, 1899. 



