824 NATURE OF MALARIA. 



That malaria is not carburetted hydrogen 

 would appear from the fact, that in coal mines 

 where it is evolved in large quantities, ague is a 

 very rare disease, but is very prevalent in low, 

 damp, and foggy situations, especially during 

 autumn, when the debilitating heat of summer is 

 succeeded by cold nights and mornings. From 

 which it might naturally be inferred that vicissi- 

 tudes of temperature are essential to a malarious con- 

 stitution of the atmosphere. And notwithstanding 

 the assertion of Dr. Caldwell, that carbonic acid 

 does not exist in unusual quantities in malarious 

 districts, it is certain that of all the morbific exha- 

 lations from decaying vegetable and animal matter, 

 it is by far the most abundant ; and that when 

 accumulated in large quantities, it is capable of 

 producing the most fatal forms of fever. 



For example, it is recorded in several works of 

 high authority, that in the year 1775, one hundred 

 and forty-six British soldiers were shut up in a 

 dungeon called the black hole of Calcutta, which 

 was eighteen feet square, open to the west only by 

 two small windows, that were strongly barred with 

 iron, and from which they could receive but a small 

 supply of fresh air, that in the course of one hour, 

 or at nine o'clock in the evening, respiration be- 

 came difficult, followed by raging delirium, and 

 before eleven o'clock, by the death of about fifty 

 men. At six o'clock in the morning, only twenty- 

 three remained alive ; and what deserves our spe- 



