910 



SCIENCE. 



[N. S. Vol. XXI. No. 546. 



and to no other science, excepting only 

 medicine itself, is public health science to- 

 day more indebted than to engineering 

 science. I have referred above to the con- 

 struction of the first municipal filter at- 

 tached to a public water supply as that of 

 the Chelsea Company of London, con- 

 structed in 1829. How different is it to- 

 day ! Not only nearly the whole of Lon- 

 don, but also Berlin and Hamburg, and a 

 thousand lesser cities all over the civilized 

 world, are now protected more or less per- 

 fectly from epidemics of typhoid fever, 

 Asiatic cholera and other water-borne dis- 

 eases by vast municipal filters, ingenious 

 and scientific in design and costly in con- 

 struction, the work of skillful and faithful 

 engineers, and monuments, more precious, 

 if less enduring, than brass, to the con- 

 tributions of engineering science to public 

 health science. Innumerable storage reser- 

 voirs and vast distribution systems for sup- 

 plies of pure water also bear witness to the 

 enormous debt which public health science 

 owes to engineering science, as do proper 

 street construction and, still more, those 

 splendid systems of sewerage with which 

 so many modern cities are equipped, and 

 which not only serve to remove quickly the 

 dangerous liquid waste of human and ani- 

 mal life, but also keep low and wholesome 

 the level of the ground water, reducing 

 dampness and promoting dryness of the 

 environment, and thereby strengthening 

 that physiological resistance by means of 

 which the human mechanism fights against 

 the attacks of infectious disease. Nor do 

 the services of engineering science end here, 

 for the fluid content of the sewers must 

 always be safely disposed of, and sewage 

 purification is to-day a problem of engi- 

 neering science no less important or diffi- 

 cult than that of water piirification. These 

 same processes of the purification of water 

 and sewage are matters of so much moment 



in public health science that in almost every 

 country experiment stations are now main- 

 tained at public and private expense for 

 the purpose of working out the most prac- 

 tical and most scientific methods of purifi- 

 cation. 



In no respect have the services of engi- 

 neering science to public health science 

 been more conspicuous than in the applica- 

 tion and the further study of the principles 

 involved in the processes of water purifica- 

 tion. It has lately been shown, for ex- 

 ample, that the introduction of pure water 

 supplies has in many cases so conspicuously 

 lowered the general death rate as to make 

 it impossible to escape the conclusions (1) 

 that the germs of a greater number of in- 

 fectious diseases than was formerly sup- 

 posed are capable of prolonged life in, and 

 ready conveyance by, public water sup- 

 plies, and (2), as a promising possibility, 

 that as the result of the greater purity of 

 the water supply the physiological resist- 

 ance of the consumers of pure water sup- 

 plies is enhanced, in some manner as yet 

 unknown ; the net result being that the gen- 

 eral death rate is lowered to such an extent 

 as to lead to a rapid increase of population 

 in communities previously stationary or 

 multiplying far less rapidly. In the case 

 of the city of Lawrence, Mass., for example, 

 I have recently had the privilege of exam- 

 ining the results of studies by the dis- 

 tinguished hydraulic and sanitary engi- 

 neer, ]\Ir. Hiram F. Mills, which show that 

 since the introduction of a municipal filter, 

 which purifies the water of the J\Ierrimac 

 River supplying water to the citizens of 

 Lawrence, while the population has in- 

 creased nearly seventy per cent., the total 

 number of deaths remains about the same 

 as it was ten years ago. Mr. Mills con- 

 cludes from the results of his studies— and 

 I see no escape from his conclusions— that 

 the introduction of the municipal filter has 



