458 Proceedings of the Royal Irish Academy. 



Conclusions from the preceding ohservations. 



Prom the preceding observations in the field and in the laboratory 

 it may fairly be inferred that — 



Peaty colouring matter seems not to be removed by direct oxida- 

 tion ; this appears specially from the Carawaystick brook, where excep- 

 tional facilities occur for oxidation, and no peaty tributaries enter along 

 that portion of the stream where it is lashed into foam down a height 

 of about 700 feet. 



Oxidation may plaj^ a certain part in precipitating peaty colouring 

 matter, in so far tlaat a ferrous salt, on becoming oxidised, carries down 

 with it the peaty colouring matter ; this appears to be an important 

 factor in the decolourising of peaty streams ; waters that are charged 

 with ferrous carbonate flowing into them have the iron precipitated, 

 the peaty colouring going down with it. 



Ferrous sulphate also acts as an efficient decolouriser, but its occur- 

 rence must be comparatively rare; however, in the Ovoca river it plays 

 an important part, and it is the most active agent in the clay specimen -4 ; 

 in the other specimens experimented upon it is the combined oxides 

 of iron and aluminum, with manganese to a less extent, that appear to 

 be the active ingredients : what their action on the peaty colouring 

 matter may be has not been determined, but in ordinary peaty water there 

 seem to be at least two distinct colouring substances ; the one gives to 

 the water a brown tint, which is comparatively easily removed, the 

 other, only to be remarked when the brown has disappeared, gives it a 

 greenish hue, which it is difficult to get rid of. 



The peaty colouring is precipitated to a greater or less extent by 

 either hydrochloric, nitric or sulphuric acids, more especially the 

 last; it has also been found, as far as the experiments have gone, that 

 salts having acid reactions act similarly, and some organic acids to a 

 less extent. 



"When these observations were commenced, it was not anticipated 

 that frost or dry weather would have had much effect upon the peaty 

 colouring of streams. Why such is the case seems somewhat difficult 

 to explain, especially as the experiments in the laboratory seem to 

 prove that the peaty colouring is not precipitated by freezing. 



Aiter a long continuance of dry weather the waters in the streams 

 and rivers are derived not from surface drainage but from springs, i. e. 

 underground drainage, where the waters have been stored in the pores 

 of the rock, and slowly percolating through the joints and crevices ; 

 any peaty matter these waters might have contained after percolating 

 the overlying peat would probably be precipitated by the clayey 

 matter contained in the joints of the rock. At the same time, any 

 little drainage there might be from the peat probably collects in the 

 holes that are always to be found; here the colouring becomes deepened, 

 partly by evaporation of the water, but principally by dissolving out 

 colouring matter from the surrounding peat. This may account for 

 the reduction of tint observed after long continued dry weather. 



