EDWARDS AND GEN TIL. 849 



of mercury at 20 degrees below 0, life would be 

 extinguished in as many seconds ; for mercury is 

 above thirteen times denser than water, and has 

 a proportionally greater attraction for caloric. 



The danger arising from exposure to a shower 

 of rain, getting the feet wet, remaining in wet 

 clothes, sleeping in damp sheets, or being out in 

 cold or moist night air, are owing entirely to their 

 abstraction of vital heat from the body. And that 

 moist air does it far more rapidly than dry air, 

 will appear from the following experiments, which 

 I performed in the summer of 1840. When a 

 thermometer was raised to 90, and its bulb sur- 

 rounded with damp cotton wool at 68, which was 

 the temperature of the air, it fell 22 in seven mi- 

 nutes. When raised to 90 and placed in dry 

 cotton wool, it was thirty minutes in falling to 68. 

 It was also found by M. M. Edwards and Gentil, 

 that by keeping one hand immersed for some time 

 in ice cold water, the temperature of the other 

 hand was reduced 11. Thus it is, that by expo- 

 sure of the feet, hands, and neck, to cold winds 

 and wet, a portion of vital heat is abstracted from 

 the blood of the whole body, during its circulation 

 through those parts, and many fatal diseases 

 brought on before we are aware of any danger. 



It is a matter of the highest practical impor- 

 tance to comprehend distinctly why it is that the 

 cold bath is invigorating, and in what states of the 

 system it is indicated. We are told by medical 



