598 Proceedings of the Royal Irish Academy. 



In tlie next two analyses on the Table (JS'os. YIII. & IX.) there is a 

 very marked difference in the organic constituents. The waters were 

 taken from the Ovoca riyer at two points — Tigroney weir and "The 

 Black Dog" — aboutthree miles apart, and with a fall of only 50 feet. On 

 comparing the two, it is evident that the conditions in the intervening 

 portion of the river are favourable for the removal of the peaty im- 

 purities. The most marked peculiarity in this part of the river is the 

 mineral drainage (largely impregnated with sulphates of iron and alu- 

 mina) that enters it, consisting of a number of small streams, which, 

 taken together, form only a small fraction of the total volume of the 

 main river; nevertheless, the organic carbon is reduced from 0"230 at 

 Tigroney to 0-095 at "The Black Dog," or to less than half that pre- 

 viously present. The organic nitrogen suffers a reduction also, but not 

 to the same extent : while, on the other hand, the total solids have 

 largely increased; viz., from 4"88 at Tigroney to 9'26 at the "Black 

 Dog," or nearly double. 



In selecting streams from which to obtain aerated samples it was 

 necessary that, between the points at which the samples were taken, 

 there should be no alteration of circumstances likely to affect the 

 waters, except simple unaided aeration : both the rivers from which 

 samples were obtained (Dargle river and Carawaystiek brook) are of 

 very soft water, and, unfortunately, samples of hard water, affected only 

 by aeration over a steep fall could not be secured ; the Doonass fall, on 

 the Shannon,* was visited and samples collected on both sides of the 

 river, above and below the falls, but the results were most unsatis- 

 factory, as there was a greater difference between the two samples fi'om 

 opposite banks, above the falls, than between either of these samples 

 and those taken from below the falls. The analyses are given at the 

 end of the Table (^os. X.-XIII.) 



In collecting the samples and in making the analyses, exceptional 



It is remarkable that in winter tlie rivers shovv very little peaty colouring. All 

 through last winter this was the case (although there was an absence of frost 

 and snow) ; but the rains towards the end of March brought down much peaty 

 colouring : this probably may be due to the retui-n of vegetation, which is early this 

 spring (18S2). 



* On writing about the floods in this river to my father, who lived for some 

 years in this neighboui'hood, part of the time at Castleconnell, I received the follow- 

 ing note : — 



' ' In the Shannon, between Eillaloe and Castleconnell, the flood waters fi-om 

 the counties of Tipperary and Limerick, on the S.E. and S., are 'black floods' 

 (peaty water), especially those that flow into it between O'Brien' s-bridge and 

 Castleconnell; whale the flood Avaters from the Clare side, to the N. and N."W., 

 except the stream from O'Brien's-bridge bog, are ' red flood, highly charged with 

 the red muds from the debris of the red basal Carboniferous shales. These different 

 classes of flood may differently affect the water at the Falls of Doonass. If rain 

 falls only in the counties of Tipperary and Limerick, there will be a ' black flood ' 

 over the falls ; while, if the rain falls only in the county Clare it will be a ' red 

 flood ' ; but if the rain is falling at both sides of the Shannon, the results wiQ be 

 very different. If, during such a rain-fall, you stand at the World's End weir, 

 CastleconneU, the flood on the Limerick side wUl be black, and that on the Clare 



