28 BURTON WATERS—DRINKING AND BREWING. 
Returning to the consideration of our Burton brewing 
waters, it may be of interest to youif I briefly refer to the 
sources of the various salts found in these waters. 
Ist. The carbonates of lime and magnesia are dissolved 
out as the carbonated rain water passes through the soil and 
beds of gravel, marl, and sandstone, all of which contain 
more or less carbonate of lime and magnesia. 
2nd. The sulphates of lime and magnesia are taken up 
by the water in the beds of gypseous marl. 
3rd. The nitrates of calcium, magnesium or sodium are 
a result of the decomposing organic matter, more especially 
sewage—acting upon carbonates of lime, magnesia, and 
soda, in the surface soils and gravel beds, and I have 
frequently observed waters which showed an _ increasing 
quantity of nitrates show a decrease in the quantity of 
carbonates. 
Within the Borough, this increase in the quantity of 
nitrates during recent years is most probably due to the 
infiltration of sewage through the old irregular sewers 
which were made at a time when the height of the water 
in the gravel beds prevented them being laid at a lower 
level; the average height of the water being as I have 
previously explained gradually lowered, these drains sank in 
some places more than others, and then became leaky, the 
sewage containing nitrogenous organic matter and ammonia, 
filtered through the sand and gravel, and the nitrifying 
bacteria quickly oxidized this nitrogen, into, first nitrous 
acid and then nitric acid, which immediately combined to 
form nitrites and nitrates respectively, and as such appeared 
in many of the shallow wells, more especially those not 
made to keep out the top waters. 
4th. Chlorides, which are usually considered as indica- 
tive of sewage contamination, are not necessarily so, and 
in fact, with the knowledge we have as to the presence 
of a salt-bearing bed of marl outcropping at Branstone, 
