76 REPORT — 1851, 



whilst even a few inches below there was no colour removed from the sand. 

 There was another circumstance to be mentioned, that the water coming from 

 the lower strata had no taste of peat, whilst that coming from the upper strata 

 had. The whole surface might be taken as an instance of a great filtering 

 bed ; but it is very remarkable that the filtering did not appear to be gradual, 

 but instantaneous ; the sand did not gradually become redder on going down, 

 but it was red at once, and did not ciiange. The organic matter seems to be 

 removed at a certain point, and not to go below it. A few inches below the 

 soil there was to be seen a black band running all along the country, I might 

 say, and I dare say most persons will have seen something similar where peat 

 lies on sand. The blackness was evidently caused by a constant deposit of 

 dark peaty matter on the point of filtration, as it may be called. There were 

 cases in which the water Howed over the bare sand, and then the blackness 

 was on the surface of the sand ; where there was vegetation, it was below the 

 roots. This black matter along with the sand looks like a sand and charcoal 

 filter. The same may be seen to a less extent on land which has not been 

 ploughed up for some time, a mark running along under the soil where 

 colouring matter seems to have been deposited. We may very correctly look 

 on the soil as the greatest agent for purifying and disinfecting. Every im- 

 purity is thrown upon it iu abundance, and yet it is pure, and the breathing 

 of air having the odour of the soil, lias, on what evidence I dnn't know, but 

 evidently with truth, been considered wholesome. Whatever may be taken 

 up by the soil the water is discharged clear, and although vegetation does its 

 part, we do not wait the return of the season to remove impurities from the 

 air above the soil ; they are laid on in autumn, but do not disturb us. The 

 purity of drainage water has been observed long ago, so that 1 do not pretend 

 to advance a novelty; and we find in Loudon's Cyclopaedia of Agriculture, 

 that " Marshall, seeing the formation of natural springs, and observing the 

 effect of subsoil drains, and being at the same time aware of an objection to 

 roof-water, which, though more wholesome, is seldom so weli-tasted as spring 

 water, was led to the idea of forming artificial land-springs to supply farm- 

 steads with water in dry situations. He proposed arresting the rain-water 

 that has filtered through the soil of a grass ground situated on the upper side 

 of the buildings, in covered drains, clayed and dished at the bottom, and par- 

 tially filled with pebbles or other open materials, thus conveying it into a well 

 or cistern, in the manner of roof-water, and by this means uniting, it is pro- 

 bable, the palatableness of spring water with the wholesomeness of that which 

 is collected immediately from the atmosphere." 



Besides this action of the soil, there is the chemical action by which wells 

 get filled with carbonic acid ; and water percolating through underground 

 strata becomes aerated by oxygen or by atmospheric air, and thus nitric 

 acid is formed. It is known that many substances in the act of decomposition 

 cause the union of oxygen and hydrogen, and in doing this some of the oxy- 

 gen is used for the formation of carbonic acid. This is a sufficient source of 

 the carbonic acid found in water, where time' and opportunity is given, such 

 as in passing through deep strata; and when we suppose it pressed into 

 the water by the mechanical force, such as is found in capillary and surface 

 action, we have in nature a close resemblance to the artificial plan of prepa- 

 ring soda and aerated waters. Sharp sand has been found to be most suitable 

 for the passage of water, and sharp pieces of glass have been found to cause 

 the union of oxygen and hydrogen more readily, and at a lower temperature 

 than rounded pieces. If the wells get their carbonic acid in this way, that is, 

 from the decomposing organic matter, the very impurities of the soil become 

 the greatest elements in purifying the water, and in rendering it palatable 





