374 Mr Cobbett, On the Heat generated by 



The experiments just related show that when dry organic 

 fibrous matter comes in contact with steam, heat is generated, 

 and the temperature of the material rises above that of the 

 steam. The following experiment shows that exactly the opposite 

 condition of affairs prevails when these materials in their ordinary 

 condition are placed in dry steam. Rolls of cotton or woollen 

 bandages each containing a thermometer were placed in a current 

 of unconfined steam which had been superheated by passing 

 through a hot copper pipe. The temperature of the steam within 

 the chamber was thus raised to 200° — 250° C. or more, and was 

 frequently high enough to scorch the surface of woollen materials 

 exposed to it. Nevertheless when rolls of fibrous material were 

 placed in this superheated steam, the thermometers within them 

 did not exceed 100° C, for as long a time as the observation 

 lasted, namely an hour or more. This result was obtained when 

 asbestos, as well as when paper, cotton or flannel was used. In 

 some cases a rise of temperature a few degrees above 100° did 

 indeed take place, but in others it remained exactly at the 

 boiling point of water. It therefore seemed probable that in the 

 former instance superheated steam must have found direct access 

 to a portion of the thermometer bulb through some crevice in the 

 material. 



The failure of the little rolls of fibrous material to attain the 

 temperature of the surrounding steam within the time limits of 

 the experiments was no doubt due to the evaporation of water 

 held in some way by the fibres ; thus causing the superheat of 

 the steam which penetrated the roll to be converted into latent 

 heat, and stored in the steam thus generated. It moreover 

 appears that this water was distributed mechanically over the 

 surfaces of the fibres, and not combined chemically with their 

 substance, because the phenomenon appeared both when asbestos 

 and when organic fibres were used, and it has already been shown 

 that dry asbestos does not combine with water with evolution of 

 heat as the other substances used do, and because the process 

 occurred precisely at 100° C, thus indicating that no energy was 

 required to separate the water from the fibre. 



It is probable therefore that in the case of fibrous materials, 

 whether they are composed of organic or inorganic matter, one 

 has to do with water mechanically spread over their surfaces, 

 which prevents them for a considerable time from attaining a 

 temperature above 100° C, when surrounded by superheated 

 steam, and which at once converts the superheated steam which 

 penetrates into their interstices into saturated steam. And 

 further it is probable that in the case of fibrous materials of an 

 organic nature, one has to do with water united in some chemical 

 manner with their substance, and that the affinity which these 



