Proceedings of the Polytechnic Association. 1021 



than the Clyde-built ships now running. The inclining of the tubes 

 in the Wilcox boiler he thought objectionable. The tubes should be 

 vertical, to take steam rapidly from the surfaces. In inclined tubes, 

 with a strong fire, the steam superheats and drives the water from 

 both ends. 



Mr. J. B. Root said, whether the tubes were inclined or vertical 

 made very little difference. He believed that vertical tubes burnt 

 out faster than the inclined. 



After further discussion on the merit of the Babcoek and Wilcox 

 boiler, the meeting adjourned. 



April 14, 1870. 



Professor S. D. Tillman in the chair; Robert Weir, Esq., Secretary. 

 Professor J. Darby, of New York, read the following paper 



Oisr Malaria. 



An uninterrupted supply of air is absolutely essential to human life. 

 Two of the elements must be nearly in the same proportions. Mtrogen 

 about seventy-nine and oxygen tvv'enty-one. Besides these two there 

 are always present variable proportions of watery vapor and carbonic 

 acid. In addition to these constant elements, there are many that 

 are sometimes present, but not always, viz., ammonia, nitric acid, 

 hydrocarbons, and generally all volatile materials exposed to the air. 

 Malaria, perhaps not volatile of itself, is often in the atmosphere. 

 This material is the subject for our present consideration. Hippo- 

 crates says that every sickness has its natural cause, and when there 

 is no natural cause, no disease can exist. According to the same 

 author, most of the disturbing influences of human health come 

 from the air. Many of the directions in Moses' sacred writings have 

 direct reference to hygienic conditions of the air, 



Hippocrates classified the conditions of human health into airs, 

 locations, waters and food, and a better classification could not be 

 made at the present time. If these conditions are favorable, health 

 follows, and the human machine wears out by its own limitations. 

 Its original constitution to resist its own action, is the meaning of its 

 durability. 



We thus see that at the time of the writings of Moses, 1,500 years 

 before Christ, and in the times of Hippocrates, years before Christ, 



