422 THE POPULAR SCIENCE MONTHLY. 



portions of India. The severe and fatal fevers prevailing in Burdo- 

 wan, Lower Bengal, during the last fifteen or twenty years, have been 

 coincident with obstruction to the natural drainage from mills, and 

 blockage of water-courses. The same cause has doubtless operated 

 to a great extent in producing the fevers of Bloomingdale, Manhat- 

 tanville, Yorkville, and Harlem. The establishment during the past 

 five years of extensive subsoil drains in those portions of New York 

 has had a visible tendency to diminish the area of malaria. A similar 

 result on a larsje scale has been noticed in Lincolnshire and other 

 parts of England, where many malarious tracts have been rendered 

 quite healthy by similar measures, having for their object the low- 

 ering of the subsoil water-level by an increased outflow. 



I have thus far confined my observations to endemic malaria. But, 

 like other diseases dependent upon telluric or organic emanations, 

 miasmatic fevers occasionally assume an epidemic character, and, 

 breaking loose from their native haunts, overspread a wide extent 

 of territory. Thus, as Hertz informs us, nearly the whole of Europe 

 was invaded by such epidemics in 1558 in 1678-79 from 1718 to 

 1722 from 1824 to 1827 and from 1845 to 1848. The cause of 

 malaria being thus propagated is as mysterious as that of most epi- 

 demics. It is possible that such an epidemic malarial influence 

 has been prevailing here; but we must not lose sight of the fact 

 that sporadic cases of malarial fever appearing in non-malarial dis- 

 tricts can frequently be traced to previous exposure in an infected 

 locality. 



Malaria, although having its ordinary habitat in low-lying re- 

 gions, may under conditions favorable for its production exist at great 

 elevations. On the Tuscan Apennines it is found at a height of 1,100 

 feet above the sea ; on the Pyrenees and Mexican Cordilleras, 5,000 

 feet ; on the Himalayas, 6,400 feet ; on the island of Ceylon, 6,500 

 feet; and on the Andes, 11,000 feet. Sometimes, however, at con- 

 siderable elevations it is unaccountably absent under circumstances 

 apparently supplying every condition for its development. Thus, 

 according to Jourdanet, close to the city of Mexico lies the lake of 

 Tescudo, some twenty-five square miles in extent, composed partly 

 of fresh and partly of brackish water, with a clayey bottom often 

 laid bare over large areas as the result of evaporation under a tem- 

 perature of 122 to 140 Fahr., notwithstanding which, malarial fevers 

 seldom occur in its vicinity. At Puebla, Mexico, on the other hand, 

 is a very malarious marsh 5,000 feet above the sea. Under ordinary 

 circumstances, a certain altitude affords immunity from malaria, 

 although low elevations of 200 or 300 feet above a miasmatic 

 tract are often more dangerous than the flat lands the poison seem- 

 ing to float upward and become intensified. This was long no- 

 ticeable on the heights of Bergen Hill, West Hoboken, and Wee- 

 hawken, which overlook the Jersey flats. At present, the elevation 



