452 Proceedings of ilie Royal Irish Academy. 



murtagli and Ballygahan mines. In a sample of water taken at the 

 tail of the Landers, a litre of water was found to contain 0'81 grammes 

 ferrous sulphate, and 0-78 grammes sulphate of alumina (equivalent 

 to 56'8 grains ferrous sulphate, and 54-7 grains sulphate of alumina, 

 per gallon), besides small quantities of arsenic and sulphate of cop- 

 per, &c. 



A sample of water taken from the Ovoca river, below, or after it 

 had received these mineral waters, was very peaty when collected, 

 and slightly turbid, but on standing some time a brown precipitate 

 settled, with a considerable reduction of the tint ; on another occasion, 

 when the river was not so deeply tinted, by allowing a sample to settle 

 for a time, the peaty colouring was completely removed, and in the 

 laboratory about five cc. of the Ballygahan water cleared 250 cc. of a 

 very peaty water ; a dark brown precipitate first settling down, then 

 a yellowish precipitate of ochre. 



AH along the Ovoca river, from the mines to its mouth in Arklow 

 harbour, there is a ferruginous ochre deposited in the pools and on 

 the stones ; this being probably due to the ferrous salts in the waters 

 becoming oxidised, this precipitation being accompanied by a consider- 

 able reduction of the peaty colouring matter in the river. A sample 

 of water taken from the river below the place where this mine drainage 

 enters is always found to contain a very finely divided precipitate of 

 ochre which shortly settles out. 



Though the Ovoca river is usually peaty, particularly during flood, 

 it was remarked that in frosty weather, and when there was snow on 

 the mountains, the peaty colouring was much, reduced, and often 

 entirely removed; the same was noticeable after a long continued 

 drought, the river running perfectly colourless above the mines. 



SJxperiments with Peaty Waters. 



These experiments, commenced in the spring of 1880, and carried on 

 under the direction of Professor Hartley, P.E.S.E., in his laboratory 

 at the Eoyal College of Science for Ireland, had for their object the 

 determination of the agents that may effect the decolourisation of peaty 

 waters, more especially of those that actually effect it in nature. 



As clays occur in some form or other along the beds and banks 

 of most streams, and as during floods they become suspended in the 

 waters to a greater or less extent, some of the first experiments were 

 made with such clays. 



Specimens were obtained, principally from the County Wicklow, 

 of disintegrating argillaceous rqcks and clays ; many of these, however, 

 were subsequently rejected, as it was found that they contained organic 

 matter sufficient to discolour the water and obscure their action on the 

 peaty colouring matter in it. 



In each experiment a measured quantity of water was shaken up with 

 a weighed quantity of clay, then left to allow the substances in suspen- 

 sion to subside. When the water had cleared, a portion was decanted 

 off and placed in a tall narrow cylinder; in some of the experiments 



