328 T)r Davy's db^v^lfs <:»< thr 



• n \ i r id i! x I abixo; < yd 



m the beds of many o£ the small streams emptying themselves 



into Lough Oured, and the Lake Singalla, '.. ., 



The methods by which I have ascertained the nature of the 

 colouring matter, are of the simplest kind. I shall briefly 

 mention them, as without such aids, merely by inspection, 

 the quality of the matter imparting the adventitious colour 

 could hardly be determined. The principal means I have 

 employed have been an acid, — strong muriatic, the blow- 

 pipe, and the microscope. Immersed in the acid, proof is 

 afforded of the presence of black oxide of manganese by the 

 solution of the colouring matter investing the pebble or frag- 

 ments of rocks subjected to the trial, and by the evolution of 

 chlorine ; and of peroxide of iron by a slower solution of the 

 colouring matter, without the disengagement of chlorine, 

 but with the production of the odour belonging to the per- 

 chloride of iron in solution. Under the microscope, the struc- 

 ture of the vegetable matter is distinctly brought into view : 

 whilst by the blow-pipe, the former is either destroyed, or if 



the apparent structure be retained, it is as a skeleton in the 

 ._ rr . t9YJ8 to esoficJenmoiio oiO 'lovo'iori// ioi 



residual ash. 



'ICL oilj qj (iiclinn liiJLlo io 0'injxj\9o:fnoj 



I have spoken of the vegetable colouring matter being 



owing to cryptogamia in a state of decomposition, or of 

 transition into peat. This is probably true in most instances. 

 In some, the black hue may be produced in a different man- 

 ner, if not natural and belonging to the plant, viz., by the 

 entanglement of peaty particles amongst the green leaflets 

 and fibres of the plants. Instances of the kind I have seen 

 distinctly when examining the vegetable matter with a low 

 power, as with a one-inch object-glass ; then, some portions 

 of the plants have appeared of a healthy bright green, whilst 

 others adjoining have been quite black. Indeed, in the ma- 

 jority of instances, as seen under the microscope, the ap- 

 pearance of the vegetable matter is not uniform, but more 

 or less varied, a part only being black, — brown and greenish 

 fibres being commonly intermixed ; though, as seen with the 

 naked eye, the whole appears black. I may add in confirma- 

 tion that the line used in fishing in these lakes had acquired, 

 even in a few days, a grey discolouration. 



In a former note, I nave supposed the black stain imparted 



