1886.] NEW YORK ACADEMY OF SCIEN"CES. 57 



Mr. Lucius Pitkin spoke as follows: 



In his closing remarks, Dr. Leeds has referred to filters in- 

 tended for household filtration on a small scale. The import- 

 ance of this branch of water purification may be better realized, 

 when it is considered with what care the source of Avater supply 

 for large cities is selected, as compared with the supply in the 

 suburbs and country towns. Here purification on a large scale 

 is impossible in the absence of a co-operation, which is hard to 

 secure, and while doubtful water should be avoided, still cases 

 are not uncommon where no recourse is possible except to sup- 

 plies more or less suspicious. 



Proceeding on the germ theory of disease (now almost proven 

 in its entirety), two methods of improvement for household use 

 are prominent. 



The one by boiling the water kills the germs, the other by fil- 

 tration seeks to remove them. The first method by driving 

 out the dissolved air renders the water flat and insipid. The 

 second method has in the past been the cause of nearly as much 

 harm as good. It is only within the last few years that, with 

 our increasing knowledge of the character of disease germs, ade- 

 quate filtration devices have been introduced. A bit of sponge 

 in a metal globe may entrap " rotifers " and " entomostraca,^' 

 but disease germs with their minute dimensions may easily 

 laugh it to scorn, or in its accumulated debris find a fit breeding 

 ground. And here I would emphasize the necessity of frequent 

 cleansing in all forms of filtration apparatus. The increased 

 volume of flow of the clean surface over that clogged with or- 

 ganic debris will, apart from sanitary considerations, repay the 

 slight trouble incident to the cleaning. 



It has been my good fortune, during the past six months, to 

 have made many and rigorous tests of the value of porous porce- 

 lain in arresting the passage of bacteria contained in water. 

 The porcelain tubes with which my experiments have been con- 

 ducted, were of about one-tenth of an inch in thickness. It 

 will be sufficient here to indicate briefly the result arrived at in 

 my latest experiments on a set of four tubes. Under a pressure 

 of about four feet, and with a continuous flow of water day and 

 night, all of the tubes were delivering germ-free water at the 



