IN THE PUREST WATERS FROM TERRESTRIAL SOURCES. 42] 



An excellent illustration was afforded by the well-known spring of St An- 

 thony's well, at the foot of Arthur's Seat, near Edinburgh. The water of this well 

 may be considered as a very pure spring- water, as respects inorganic constituents ; 

 the ordinary tests shewing very feeble reactions with it. On the other hand, 

 acetate of lead produces in it, whether before or after being boiled, a dense white 

 cloud, dissolved without effervescence, by a drop or two of nitric or acetic acid, 

 and no farther precipitate, insoluble in acetic acid, is afterwards formed ; in short, 

 whilst in comparison with many other waters, its inorganic purities are insigni- 

 ficant, its proportion of organic matter is notable. 



There could be little doubt, that the origin of this organic matter in pure 

 water was to be referred to the decomposition of vegetable matter contained in the 

 strata and soil through which the water had infiltrated, or otherwise had its pas- 

 sage. I therefore could have wished to examine some spring at a considerable 

 elevation, and having as rocky a source as possible, with the view of ascertaining 

 to what extent it might still contain such a constituent ; but during the course of 

 these investigations, I had not an opportunity of visiting any more elevated spring 

 than one about two-thirds of the way up the hill of Arthur's Seat, or, by barome- 

 tric measurement, 522 feet above the level of the sea. This spring issues from 

 the trap-rocks on the NW. face of the hill ; but, of course, there is vegetation scat- 

 tered on their surface. Accordingly I found the organic matter in its water, al- 

 though to a less extent than in St Anthony's spring at the foot of the hill. 



We may anticipate, that if a spring were examined on any elevated moun- 

 tain, at a height entirely above the limits of any vegetation, we should cease to 

 find this substance. A similar observation may be made respecting the water 

 directly issuing from snow and glaciers. I have already stated, that in rain-water 

 it does not exist. Such water, if collected with ordinary care and boiled a few 

 minutes, is entirely unaffected by the acetates of lead. 



It will readily occur, that on the supposition that this matter exists to a 

 greater or less extent in all waters which have infiltrated through strata be- 

 low the limits of vegetation, it must necessarily perform a part of considerable 

 importance in the economy of nature. Being in solution in water, it is evidently 

 in that state which is best adapted for being taken up by the roots and fibres of 

 plants, and so contributing to their nourishment, in so far as that nourishment 

 has access by these channels. May not a part of the beneficial effects of irriga- 

 tion be due to such dissolved organic matter ? Even as regards the animal eco- 

 nomy, we cannot suppose that it will not contribute, in proportion to its amount, 

 to the nourishment of man and other animals partaking of such waters ; and this 

 will more particularly be true, if it really be an azotized body. 



ST ANDREW'S, 8th March 1843. 

 VOL. XV. PART III. 5 X 



