THE PRESIDENTIAL COLD AIR MACHINES. 295 



RELATION OF FOUL AIR TO CONSUMPTION. 



" Experiment has shown that if an animal be kept confined in a narrow, 

 closed apartment, so that the air supplied is always more or less vitiated by the 

 carbonic acid which it expires, however well fed that animal may be, tubercle 

 {consumption) will be developed in about three months." If this be the case, a 

 large percentage of cases of consumption should be met with among the inmates 

 of badly ventilated schools. But, fortunately, the disease is comparatively infre- 

 quent under the age of fifteen, and added to this is the protecting influence of 

 the active exercise in the open air usually indulged in by school-children. It is 

 upon the teachers that its blighting effects are most apparent, as they are predis- 

 posed by age, they neglect exercise in the open air, and their mental labor is se- 

 vere, and worry of mind exhausting. Of eleven teachers who died during the last 

 eight years within the limits of one county in Pennsylvania, two died of acute 

 disease, one of an overdose of an habitual narcotic, and of nine attacked by con- 

 sumption, eight died — six ladies and one gentleman; the other, a gentleman, will 

 recover, at least for a time. — Ft cm " Schoolroom- Ventilation" by Dr. P. J. Hig- 

 gins, in Popular Science Monthly. 



SCIENTIFIC MISCELLANY. 



THE PRESIDENTIAL COLD AIR MACHINES. 



The apparatus which proved most satisfactory in cooling the chamber of the 

 wounded President, was furnished by a Mr. Jennings, of Baltimore. It was de- 

 vised for use in a new process of refining lard. According to the inventor's 

 description the apparatus consists of a cast iron chamber, about ten feet long, 

 three wide and three high, filled with vertical iron frames covered with cotton terry 

 or Turkish toweling. These screens are placed half an inch apart, and represent 

 some three thousand feet of cooling surface. Immediately over these vertical 

 screens is placed a coil of inch iron pipe, the lower side of which is filled with 

 fine perforations. Into a galvanized iron tank, holding loo gallons of water, is 

 put finely granulated or shaved ice (and salt when a low temperature is required). 

 This water is sprayed upon the sheets in the lower tank constantly. In each end 

 of the iron chamber are openings thirteen inches square. To the outer end of 

 this chamber is a pipe connecting with an out-door air conductor. To the oppo- 

 site end is connected a similar pipe leading into an ice chamber at its top, and 

 from the bottom of the same a pipe leads to a small exhaust fan, and from the fan 

 the now cold and dry air is forced direct into the President's room through a flue 

 some twenty feet in length. Air at 99° temperature today is supplied at the rate 

 of 22,000 cubic feet per hour at the register in the President's room at 54°, and 



