SAFETY IN HOUSE-DRAINAGE. 295 



It is at this point that the serious error of a false assumption 

 is so frequently made. The truth is, that sewer-air does not come 

 into our houses in any appreciable quantity through the water- 

 seals of traps. On the contrary, it passes through the trap when 

 the seal has been lost — when the water has been accidentally 

 withdrawn or forced out. The broad principle of the efficiency of 

 water-seals is not affected by these apparent failures. The diffi- 

 culty is in maintaining the seals — in keeping them intact and 

 secure against all the various adverse influences that may affect 

 them. And here the aid of sanitary science must be sought ; for 

 the plumber's art has been powerless to devise traps that will pro- 

 tect our houses from the foul air of the sewers. Every failure in 

 this attempt has been from a disregard of principles that have 

 been well established by competent authorities. What are these 

 principles ? 



For many years, skillful chemists, devoting themselves to sani- 

 tary work, have been carrying on careful investigations regard- 

 ing the possibility of the passage of sewer-air and disease-germs 

 through the water-seals of traps. The definite determination of 

 this question is necessary in order to establish proper means of 

 defense against the dangers we have already considered. It is 

 evident that the form of traps and other apparatus to be used for 

 this purpose will depend upon a conclusive demonstration of the 

 truth or falsity of the views of those who have maintained that 

 water as a resisting medium gives no protection in this par- 

 ticular The evidence which we have upon this point is clear 

 and conclusive. 



As long ago as 1877, Naegeli, an eminent scientific authority 

 in Munich, established conclusively that disease-germs can never 

 be given off from a liquid at rest in any ordinary temperature. 

 Later researches by Carmichael, Wernich, and Miquel, chemists 

 and sanitarists of world-wide reputation, corroborated the truth 

 of Naegeli's demonstrations in every respect. 



In 1880 the United States National Board of Health, through 

 the efforts of Colonel George E. Waring, Jr., secured an appropri- 

 ation for the purpose of investigating the same subject. Two able 

 chemists. Prof. Raphael Pumpelly and George A. Smyth, Ph. D., 

 were employed to conduct the investigations. A long series of 

 careful and delicate experiments was made, extending through 

 several months, and the published report of the results forms a 

 valuable contribution to the literature of sanitation. The conclu- 

 sions in this instance are precisely the same as those of the other 

 authorities above referred to — viz., that disease-germs can not be 

 given off to the air from any quiescent liquid at a normal tem- 

 perature. 



The experiments of Dr. Neil Carmichael, Fellow of the Faculty 



