Diving Bells and Suits 367 



These symptoms are attributed by the physicians of Douchy 

 exclusively to pulmonary, hepatic, renal, or cerebral congestions. 

 In the special chapter devoted to the enumeration of theoretical 

 explanations, we shall see what theories of these pathological 

 phenomena were given by MM. Pol and Watelle. 



I have wished to review at length their important Memoir, the 

 first study of high pressures to appear, not only because of the 

 numerous interesting observations reported in it, but also because 

 truths of great importance are clearly revealed by it: 



1. "Compression, up to 4%, atmospheres, is not dangerous in 

 itself; it is endured very well and infinitely better than a rare- 

 faction which is proportionately much less." Only the return to 

 normal pressure is dangerous; its danger is proportional both to 

 the amount of the compression and the speed of the decom- 

 pression: the decompression must therefore be very gradual; 



2. In compressed air, the venous blood becomes bright red. This 

 effect lasts a short time after return to normal pressure; 



3. We are "justified in hoping" that a sure and prompt means 

 of relief would be to recompress immediately, then decompress 

 very carefully; 



4. Chlorotic or anemic persons and those who have respiratory 

 difficulty will be benefited by a stay in air compressed to a variable 

 degree. 



During the work at Douchy, an explosion occurred at a time 

 when the total pressure was 3.20 atmospheres. It was the subject 

 of a report by M. Comte, 12 chief engineer of the mines. Eight men 

 were in the apparatus at the time; four were crushed to death; 

 two others, after beginning to climb the ladder to leave the cylin- 

 der, let go of it, without anyone ever being able to find out why or 

 how; a seventh workman felt no ill effects; the eighth, who was 

 overtaken by the water, also managed to escape. In regard to him, 

 M. Comte suggests a strange and interesting hypothesis, interesting 

 because it shows how easily the best minds go astray in these 

 questions: 



Perhaps he found some help in rising above the water .... in 

 the specific lightness given him by the compressed air with which 

 certain parts of his body were still more or less filled. (P. 130.) 



The new method quickly became general. Other shafts were 

 sunk, and data similar to those reported by MM. Pol and Watelle 

 were observed. 



That happened, for instance, according to the report of Bouhy 13 

 in the mine of Strepy-Bracquegnies (Belgium) : 



