HAMILTON SCIENTIFIC ASSOCIATION 28 



to prevent the disease is to breathe absolutely pure air. It 

 has been proved that a child requires from 2000 to 2500 cubic 

 feet of fresh air per hour, and an adult 3000 or over. In 

 many of our public halls, churches and schools not more than 

 one-tenth of that is provided for. People are crowded 

 together for hours, breathing the same air again and again, 

 coming from diseased lungs and clothing, sometimes none too 

 clean, and containing exhalations from the surface of bodies 

 that seldom receive a bath. Is it any wonder that provision 

 has to be made for them in a Sanatarium before they reach 

 the age of twenty-five ? I believe that three-fourths of the 

 cases of tuberculosis could easily be traced to bad ventilation. 



Ventilation is a difficult problem to deal with, because 

 we are dealing with a substance we cannot see. The most 

 perfect theory may be defeated by bad material, or an un- 

 skilled workman. The architect deals with the empty build- 

 ing, and seldom or never is in the building after it is occupied, 

 when the conditions are entirely different. Changes of wind 

 are so frequent and violent that no system or theory can be 

 relied on at all times. What will suit one season, direction 

 or velocity of the wind, will not suit another. The difference 

 in weight of the air at the top and the bottom of a ventilating 

 shaft may be only a few grains to cause the draught, which 

 is very often reversed. 



I shall refer specially to ventilation in cold weather, 

 as the windows generally serve for ventila tion in the 

 summer, though they were never intended for that purpose. 

 Provision should be made to admit fresh air. The openings 

 should not be too near the ground or the air will be impure. 

 It has been proved that air brought from 135 feet from 

 the ground contains only 20 per cent, of the dust and other 

 impurities, which it contains when brought from 15 feet 

 from the ground. The air should be warmed to the proper 

 temperature before it enters. It should not pass over metal 

 too highly heated, and should be diffused while entering. 

 Several openings are much better than one, it should retain 

 the proper amount of moisture. Air saturated at 20° raised 

 to 40°, would require double the aqueous vapor and 



