House and Garden 
which has held this inlet closed, to he released and 
the adjoining hed then coniniences to fill. The 
third air hell forces air into the inlet through which 
the bed has been filled and closes it. The sewage 
then remains at rest amongst the broken stone to 
which the organic matters gravitate and adhere. 
Meanwhile a second chamber has been slowly filling 
with the filtered sewage water. When a definite 
time has elapsed, and the water has risen to a certain 
level, pressure acts upon the contents of a fourth air 
hell which displaces from a U-shaped pipe water 
which has held the outlet closed during the periods of 
filling and resting full of the first filter bed. The con¬ 
fined air is thus released and the water flows out 
from the hed, freed from organic matters, spreads 
over the surf ace of the sand filter and gradually sub¬ 
sides through the sand passing into the underdrains 
and out to the stream clear, sparkling and odorless. 
While this last process is being carried out the second 
contact bed is filling, and later, precisely similar 
movements to those we have just described take 
place in the chambers of that hed. 
1 he principle upon which this method of auto¬ 
matic operation is based was first worked out in 
England, hut necessity, which is frequently the mother 
of invention, has resulted in its application in this 
country upon a more workable scale, and to the 
decided advantage of those who are responsible for 
the important feature of regularity of operation in 
the treatment of sewage. 
It will he seen that the first method applied at 
Essex Fells which proved inadequate, was that of 
automatically spreading crude sewage over an area 
of sand so that it might be purified by simple sub¬ 
sidence through the sand, and that the present 
method is to mineralize the sewage, with the aid of an 
automatic device, after preparation for this process has 
taken place by preliminary fermentation in a suitably 
constructed tank, and to make use of the sand filter. 
not for dealing with organic matters in sewage, but in¬ 
stead for the clarification of oxidized sewage water. 
The previous method necessitated that the grit 
chamber he frequently cleaned out, which operation 
was odorous and distinctly objectionable. As the 
volume of sewage increased the surfaces of the sand 
filters continually needed raking, and the beds were 
not sufficiently aerated to effect satisfactory sewage 
purification. 
By the present method the suspended matters re¬ 
main out of sight, and a large part of them is liquefied 
and gasified. Should it become necessary in the 
future to dispose of an accumulation of matters which 
are not removed by anaerobic action, these can be 
carried by gravity to the upper sandbed where the 
water which forms 90 per cent of such accumula¬ 
tion, will drain away, and when the residue can 
then readily be handled. 
The use of the present combination of processes 
requires less area than the former method (if the 
disused upper sandbed is disregarded), while it is 
capable of taking care of the continually increasing 
volume of sewage for many years to come. It is also 
more automatic in its operation, seeing that it is not 
necessary to manipulate any valves by hand, except 
at infrequent intervals. 
In claiming the reader’s attention to the facts 
stated above, we would emphasize the importance of 
bearing in mind that in the treatment of sewage 
while the diff erence in the character of sewage and of 
local conditions and requirements renders it impos¬ 
sible to point to any one method or combination of 
methods as a “cure-all” it is nevertheless true that 
whether it he in respect of the treatment of sewage 
from a single residence or of that of a large city, 
the same general laws apply, governing the most 
successful utilization of the life processes of micro¬ 
organisms, “the important, almost the only agents 
of universal hygiene. ” 
86 
