18 



SCIENCE 



[N. S. Vol. XXXIII. No. 836 



There are two general methods for disposing of 

 street dirt; namely, it may be picked up, swept 

 up, or shoveled up, and then hauled away, or it 

 may be washed into sewers through the agency 

 of water, or there may be a combination of these 

 methods." As a rule, a considerable portion of 

 the dirt is conducted away during rain storms, 

 and some cities htxve especially constructed their 

 sewers with the view of conducting off all dirt 

 which can be reasonably emptied into them; in 

 fact, it may be said that many municipal engi- 

 neers consider that the sewerage system of a city 

 should be constructed in such a way that it will 

 carry off a large portion of the fine dirt from the 

 streets. 



I will go further and say that the streets 

 should either be made dustless or wet down 

 with dilute chlorine water, that is, a solu- 

 tion of bleaching powder, or other disin- 

 fecting fluid. Both methods have been 

 used with success and are within reason- 

 able cost. 



The topography of a district in which 

 urban population has massed itself will, in 

 a measure, regulate the mode of growth. 

 Although improved methods of rapid 

 transportation have overcome the neces- 

 sity of concentration, yet business and 

 other causes continue to make for centrali- 

 zation, with consequent elevation in the 

 value of land, whose acreage is increased 

 only by vertical expansion. The modern 

 subway comes as a result. The air from 

 the streets is sucked into these human mole 

 holes. It is to be hoped that the Public 

 Service Commission will not allow the 

 construction of any more subways, or that 

 subways be built in other cities, except 

 that the tracks be separated by partitions, 

 or that the tracks of trains going in oppo- 

 site directions will be kept in different 

 compartments. These have now been in- 

 cluded in the specifications for the proposed 

 subways in Greater New York. For, al- 

 though much street air enters the tunnels in 



^ Vacuum street cleaners have so far proved to 

 be too expensive. 



New York at present, a large portion of the 

 air is simply churned by the passing trains 

 and not quickly and properly replaced. 

 The ventilation in the London Tubes and in 

 the Pennsylvania-Long Island Tunnels is 

 excellent. 



There are many incidental impurities in 

 city air that are local and more or less 

 evanescent. I have shown that in the city 

 of New York about 1,300 tons of sulphur 

 dioxide are poured into the air daily in the 

 combustion of coal. This is a sad annual 

 economic waste of a most important chem- 

 ical, some millions of dollars in value, 

 which we do not know how to avoid or save 

 at present. 



The smoke problem has confronted every 

 city where coal is used as the main fuel. 

 Civilized nations are only beginning to 

 awaken their "conscience of fuel." Our 

 methods of utilizing coal give us a return 

 of only five per cent, of its energy when 

 burned, and only one per cent, when we 

 convert that energy into electric light in 

 the city. 



Good firing is admittedly an important 

 factor in smoke prevention, and it has even 

 been regarded as the main factor of the 

 problem;' but many authorities favor the 

 distribution of gas as a means of at least 

 alleviating the smoke nuisance.' 



There have been many complaints 

 against some of the railroads running out 

 of New York City, because of the nuisance 

 caused by their use of soft coal. Some of 

 the suburban towns have taken legal action 

 to prevent this. The solution of the smoke 

 problem on the railroads reduces itself to 

 the use of hard coal or oil, as the applica- 

 tion of mechanical stokers and smoke-con- 

 suming devices to locomotive engines has 



" Caborne, Jour. Roy. San. Inst., 27, p. 142. 



' For example. Lodge, Des Voeux, A. J. Martin 

 and A. S. E. Ackerman; in this connection, see 

 Jour. Roy. San. Inst., 27, pp. 42, 64> 80, 85. 



