88 



POPULAR FALLACIES. 



likewise felt, and a still greater heat on any metallic object in the room. Walls 

 and woodwork will be felt warmer than the matting, or the clothes which are 

 put on the person. Now, all these objects are, nevertheless, at the same tem- 

 perature. From this chamber let us suppose that we pass into one at a low 

 temperature ; the relative heats of all the objects will now be found to be re- 

 versed — the matting, carpeting, and woollen objects, will feel the most warm ; 

 the woodwork and furniture will feel colder ; the marble colder still ; and metal- 

 lic objects the coldest of all. Nevertheless here, again, all the objects are 

 exactly at the same temperature, as may be in like manner ascertained by the 

 thermometer. 



In the ordinary state of an apartment, at any season of the year, the objects 

 which are in it all have the same temperature, and yet to the touch they will 

 feel warm or cold in different degrees : the metallic objects will be coldest ; 

 stone and marble less so ; wood still less so ; and carpeting and woollen ob- 

 jects will feel warm. 



When we bathe in the sea, or in a cold bath, we are accustomed to consider 

 the water as colder than the air, and the air colder than the clothes which sur- 

 round us. Now all these objects are, in fact, at the same temperature. A 

 thermometer, surrounded by the cloth of our coat, or suspended in the atmo- 

 sphere, or immersed in the sea, will stand at the same temperature. 



A linen shirt when first put on will feel colder than a cotton one, and a flan- 

 nel shirt will actually feel warm ; yet all these have the same temperature. 



The sheets of the bed feel cold and blankets warm ; the blankets and sheets, 

 however, are equally warm. A still, calm atmosphere, in summer, feels warm ; 

 but if a wind arises the same atmosphere feels cold. Now a thermometer, sus- 

 pended under shelter, and in a calm place, will indicate exactly the same tem- 

 perature as a thermometer on which the wind blows. 



These circumstances may be satisfactorily explained, when it is considered 

 that the human body maintains itself almost invariably, in all situations, and at 

 all parts of the globe, at the temperature of 96° ; that a sensation of cold is 

 produced when heat is withdrawn from any part of the body faster than it is 

 generated in the animal system ; and, on the other hand, warmth is felt when 

 either the natural escape of the heat generated is intercepted, or when some 

 object is placed in contact with the body which has a higher temperature than 

 that of the body, and consequently imparts heat to it. The transition of heat 

 from the body to any object when that object has a lower temperature, or from 

 the object to the body when it has a higher temperature, depends, in a certain 

 degree, on the conducting power of the objects severally, and the transition 

 will be slow or rapid, according to that conducting power. An object, there- 

 fore, which is a good conductor of heat, if it has a lower temperature than the 

 body, carries off heat quickly, and feels cold ; if it has a higher temperature 

 than the body, it communicates heat quickly, and feels hot. 



A bad conductor, on the other hand, carries off and communicates heat very 

 slowly, and therefore, though at a lower temperature than the body, is not felt 

 to be colder, and, though at a higher temperature, not felt to be warm. 



Most of the apparent contradictions which have been already adduced in the 

 results of sensation, compared with thermometric indications, may be easily 

 understood by these principles. 



When we pass from a hot bath into a room of the same temperature, the air, 

 though at a higher temperature than our body, communicates heat to it more 

 slowly than the water, because, being a more rare and attenuated substance, a 

 less number of its particles are in actual contact with the body ; and also such 

 particles as are in contact with the body take almost the same temperature as 

 the body, and adhere to it, forming a sort of coating or shield, by which the 



