Page:Transactions of the Provincial Medical and Surgical Association, volume 2.djvu/199

 to them, but which have been shewn to be produced by causes quite independent of the qualities of water, and to depend on morbid operations of the animal economy. The almost universal freedom of the red sandstone from noxious metals (lead and copper being rarely found in it,) adapts it for the purpose of an excellent natural filter. By its spontaneous decomposition, also, this sandstone is known to furnish an excellent sandy loam, one of the most desirable that can be found for the production of every vegetable; and in this manner it cannot but materially contribute to the salubrity of any country, of which it is the prevailing rock.”

In a medical point of view, the soil and subsoil are, perhaps, of more importance than the subjacent rock. In some parts of the low ground on which Bristol stands, the sandstone is merely covered with red loam or earth; in others, there are large deposits of alluvial clay, and peat, filling up the hollows in the sandstone. The clay is of a blue colour, and from 10 to 20 feet thick. Dr. Bright says that, on digging the channel of the New River, a bed of peat, 2 feet thick, was found, 12 or 14 feet below the surface. From the geographical account which has been given of the distribution of the rivers which intersect the city in so many directions, it might reasonably be inferred that there must be a considerable extent of alluvial matter corresponding with their course, and this is found to be the case. Thus the principal part of Temple Parish, St. Philip's, St.