SIXTH ANNUAL YEAR BOOK — PART I. 35 



is said that tlie construction of a city well in such a formation caused 

 private wells in the town to go dry. Incredible as it may seem, in the 

 case of an intelligent community, the same private wells were then uti- 

 lized as cesspools. "Wherever a cesspool is used to disiKDse of the sewage 

 of a house it should be made absolutely watertight by lining it with 

 plastered cement masonry, and as often as necessary the contents of the 

 cesspool should be pumped out and carted away. This, however, is 

 expensive and the cleaning out of such cesspools is a very disagreeable 

 task. 



In the recent development of sewage disposal the sewage is purified 

 by means of certain species of bacteria. Within the last few years it 

 has been found that one class of bacteria can be utilized in a tank some- 

 what like a cesspool, which is called a septic tank. By the way, this 

 word "septic" is sometimes miscalled "antiseptic." In the septic tank we 

 encourage the growth of bacteria instead of discouraging their growth 

 as the word "antiseptic" would mean. In the septic tank the kind ol 

 bacteria cultivated are what are known as "anaerobic bacteria", viz., 

 those which do not require air and oxygen to live. These anaerobic orean- 

 isms seize upon the organic matter in the sewage and partially break 

 it up and change it to mineral form. After a time much of the solid 

 matter in the sewage is liquified. A septic tank is nothing but a water- 

 tight tank of proper size and arranged in accordance with certain prin- 

 ciples, into which the sewage is discharged. The sewage itself contains 

 enough of the proper organisms to start them in the tank and within a 

 few weeks they become established of themselves in sufficient numbers 

 to act properly upon- the sewage. The proper size of tank for the indi- 

 vidual family is a matter upon which we are still experimenting. It 

 should probably contain three hundred to five hundred gallons. The 

 inflow of sewage should be through a vitrified pipe placed just above 

 the level of the water in the tank and turned down so that the sewer 

 will be trapped oflf from connection with the septic tank. Similarly, at 

 the outlet end some means should be provided, such as a baffle board 

 extending from above the surface a distance of fifteen to eighteen inches 

 into the sewage, to hold back all scum which forms on the surface of the 

 sewage. The tank should be made water tight and tbp opening provided 

 for cleaning it should be provided with a tight cover. 



The overflow from the septic tank usually contains a considerable 

 amount of fine inky black particles which represent part of the organic 

 matter in changed condition. In the form of septic tanks with which 

 we are now experimenting we are trying to filter out these black parti- 

 cles so as to leave the effluent more clear, and v/hile we have not yet 

 demonstrated finally that this attempt will be a success, yet as the neces- 

 sary arrangement can be provided with very little additional expense I 

 would advise using it. I present herewith a drawing with dimensions, 

 showing the details of the septic tank which, in the present state of our 

 experiments, we believe would be the best to construct. 



In the septic tank from thirty to fifty per cent of the polluting matter 

 in the sewage can be removed. A small part of this matter remains in 



