“That the permeability of the sandstone is occasionally interfered with by faults or fissures filled with argillaceous matter, sometimes rendering them partially, or wholly, water-tight. “That neither by sinking, tunneling, nor boring, can the yield of any well be very materially and permanently increased, except so far as the contributing area may be thereby enlarged. “That the contributing area to any given well is limited by the amount of friction experienced by the movement of the water through the fissures and pores of the sandstone; and “That there is little or no probability of obtaining, permanently, more than about 1,000,000 or 1,200,000 gallons a day from each well, and this only when not interfered with by other deep wells.” Statistics of the flow of the Windsor well show that the yield, in 1843, was 1,152,000 gallons per day; in May, 1848, 807,061 gallons; in January, 1850, from 705,667 to 634,752 gallons. The observations of the Green Lane well, in the same city, give the decrease in flow, per annum, at 4.7 to 6 per cent. A plan has been proposed, by Mr. Bailey Denton, that, in order to increase the water-bearing stratum under London, sufficiently for a water supply, and also secure the well-known benefits of the filtration powers of the chalk, to let the Thames water pass down to the chalk, through the London clay, by means of wells sunk or bored. The objections raised against this plan is the possibility of the wells becoming choked by accumulation of impurities. Mr. J. T. Fanning in his valuable “Treatise on Water Supply Engineering,” says: “The success of wells, penetrating deep into large subterranean basins, upon the first completion, has usually led to their duplication at other points within the same basin, and the flow of the first has often been materially checked upon the commencement of flow in the second, and both again upon the commencement of flow in a third, though neither was within one mile of either of the others. The flow of the famous well at Grenelle was seriously checked by the opening of another well at more than three thousand yards, or nearly two miles distant.” POLLUTION OF WELL WATER. It is stated that about fifteen millions of the British population live in towns and urban districts. Even if we assume, which is not yet the case, that all these people are supplied by water-works, the remaining twelve millions of county population derive their water almost exclusively from shallow wells, and these are, so far as our experience extends, almost always horribly polluted by sewage and by animal matter of the most disgusting origin.