212 Scientific Proceedings, Royal Dublin Society. 
I trust ina further communication to be in a position to give 
good reasons for regarding the colouring matters of peat, as secre- 
tions by saprophytic organisms when thriving on dead vegetable 
matters. Some two years ago I read a short note before the 
British Association Meeting at Cardiff, on the olive green, and 
brown colouring matters, which are secreted by saprophytic organ- 
isms, when grown under certain conditions in fresh town sewage. 
I found, under the conditions referred to, the fermentable organic 
carbon in fresh sewage was oxidized to carbon dioxide, and that 
ammonia was at the same time formed, which in its turn was 
oxidized to nitrous and nitric acids. The final products were 
liquids, coloured brown and greenish-brown, which underwent no 
further fermentation. The green and brown colouring matters 
were indistinguishable from similar coloured matters from peaty 
streams. 
If this explanation of the origin of the organic matters in the 
Vartry water be the correct one, we can understand at once the 
reason for their appearance in the filtered water from the works at 
Roundwood; and we can regard the chemist’s opinion that peaty 
matters, when present in small quantities in potable waters, present 
no danger to health, a safe and proper one. 
We have next to consider the character of the organic matters 
in the unfiltered water. I have already pointed out that they 
exceed slightly the limit usually allowed to good potable waters, so 
far as the albuminoid test can indicate. The point of importance 
is, is any of the organic matter in the water fermentable? We 
have a proof that fermentation must have occurred in the water at 
some time of its previous history, in the presence of the decided 
quantities of free ammonia it contained. It was accordingly a 
matter of great interest to ascertain whether (1) there were still 
present in the water any fermentable organic matter, and (2) 
whether any nitrification was going on in the water itself. 
To put these points to the test, a sample of the water was kept | 
completely out of contact with air for seven days, and again 
analysed. A sample of the filtered water was also similarly kept 
and analysed. The two analyses are given in the above table. A 
glance at the results will show no change occurred to the dis- 
solved gases, or free ammonia, in either unfiltered or filtered 
water on keeping for seven days, the slightest variation in the 
