24 POPULAR SCIENCE MONTHLY 



care is taken in disposing of waste matter that may find its way into 

 the air. No doubt more is being done in this direction than in former 

 days, but the rapid concentration of living quarters and industrial 

 shops brings with it new conditions. It should be remembered that 

 it is our pressing duty, and part of that civilization which has built 

 cities for millions, to keep them not only inhabitable, but healthful, 

 wholesome and pure. Elbert Hubbard in the course of his travels 

 once observed that ' The path of civilization is strewed with tin cans/ 

 This certainly insinuates that we have not yet arrived, while tin cans 

 and a multitude of other witnesses of neglect in civic duty are seen 

 along the path. 



The Smoke Nuisance. — Smokeless combustion is not only feasible 

 for almost any kind of coal, but more economical if properly attended. 

 The principal difficulty exists in the design of the proper furnace to 

 suit the fuel and to meet the conditions under which it is burned. 

 There ought to be no restriction on the use of bituminous or any other 

 coal. On the other hand, no excuse should be accepted for black smoke 

 from any source within city limits. If not willing or able to suppress it, 

 the offensive industry must be made to move. But all the smaller and 

 innumerable sources of medium, light and invisible smoke should also 

 receive attention. They emit, in reality, by far the largest share of it 

 in the average commercial and residential community, less noticeable 

 because more diluted, but none the less objectionable. The reduction 

 of this smoke is, for practical reasons, beyond control of local health 

 authorities, but it can gradually be eliminated through individual 

 action; that is, by the general concentration of light, heat and power 

 service. The movement in this direction was started long ago with 

 the introduction of central stations for light and power, but it is 

 capable of much greater extension, particularly for heating and power. 

 The bulk of the fuel should be burned at the mine, or at tide-water 

 outside of city limits. Such concentration of combustion for various 

 needs represents a material saving in the total amount of fuel con- 

 sumed, and, therefore, of the smoke produced. It would incidentally 

 avoid the handling of much coal and ashes and reduce the large amount 

 of exhaust steam now seen pouring away from the numerous individual 

 plants in certain neighborhoods. On still days, these vapors contribute 

 perceptibly to the murkiness of the atmosphere. The use of steam 

 power for transportation in urban and densely populated suburban dis- 

 tricts has long since ceased to be a necessary evil and should have been 

 prohibited years ago. It is gratifying to state that at last this much- 

 needed economic and sanitary reform seems about to be realized. 



Street Dust. — Dust of the streets is one of the principal elements in 

 polluting the atmosphere. It is made up of innumerable substances 

 utterly defying description. To what extent it permeates the air, even 



