276 PHYSICAL GEOGRAPHY. 



titles of woody and vegetable bodies brought down in the course of ages by the river 

 Orinoco, which, becoming arrested in particular places by the influence of currents and 

 eddies, and subject to the agency of subterranean fire in this region of volcanic action, 

 have undergone those transformations and chemical changes which produce petroleum, 

 converted into pitch upon being forced up to the surface and exposed to the air. There 

 are waters, however, unconnected with bitumen, from whose surfaces flames dart out, 

 without the liquid being at all hot. These contain inflammable gases, disengaged from 

 masses of iron, zinc, and tin, dissolved by sulphuric and muriatic acids. Such are the 

 fountains of Poretta Nuova, and a brook near Bergerac, which may be kindled by a 

 lighted straw. Similar springs have appeared near Wigan in Lancashire, and Brosely 

 in Salop, by the banks of the Severn. 



7. Mineralised. Water is seldom found in a pure state, that is, without colour, taste, 

 or odour. It is generally met with possessing these properties ; and even when its odour 

 is not cognizable by man, the keener sense of the camel will scent it afar off in the desert. 

 Rain water is impregnated with whatever foreign ingredients may exist in the atmosphere 

 through which it descends ; a x nd spring water, besides betraying the ingredients usually 

 found in the rains from which it proceeds, becomes charged with a variety of substances 

 and gases in percolating through the superficial strata of the earth. When these are 

 present in an extraordinary degree, so as to produce some sensible effect upon the animal 

 economy, the springs so constituted are termed mineral, and are both cold and thermal. 

 The mineral waters may be grouped generally into the four following classes, and occur 

 at the places annexed to them : 



Saline Aperient Waters. In Germany, at Carlsbad, Marienbad, Egra, Kissengen, 

 Wiesbaden, Baden-Baden, Seidlitz, and Pullna. In England, at Cheltenham, Lea- 

 mington, Harrowgate, Northwich, Epsom, and Ashby-de-la-Zouch. In Scotland, at 

 Dumblane and Pitcaithly. 



Alkaline Waters. In Germany, at Carlsbad, Marienbad, Kissengen, Pullna, Saidschutz, 

 Ems, Toplitz, and Wiesbaden. In England, at Harrowgate, Scarborough, Cheltenham, 

 Leamington, and Bath. In France, at Vichy and Mont d'Or. 



Chalybeate and Acidulous Waters. In Germany, at Spa, Pyrmont, Schwalbach, 

 Marienbad, Aix-la-Chapelle, and Seltzer. In England, at Tonbridge, Harrowgate, and 

 Brighton. In Scotland, at Peterhead. 



Sulphureous Waters. In Germany, at Aix-la-Chapelle. In the Pyrenees, at Bareges. 

 In England, at Harrowgate, Askern, and Kedleston. In Scotland, at Moffat and 

 Strathpeffer. The foreign sulphureous springs mentioned are hot ; the domestic, 

 cold. 



The waters of many of the chalybeate springs frequently hold in solution so large a 

 quantity of iron, as to encase with a ferruginous deposit the channels through which they 

 pass, depriving of their natural green the mosses and grasses which are laved by the 

 stream, and covering them with a yellow incrustation. The brine springs of Northwich, 

 which rise up through beds of rock-salt, are also so fully saturated, as to yield an annual 

 supply of upwards of forty thousand tons of salt manufactured from them, besides the 

 large quantity taken from the mines. But of all mineral ingredients, lime combined with 

 carbonic acid occurs in the greatest abundance in springs, some of which are thermal. 

 The deposition of the calcareous matter held in solution takes place when the acid is 

 dissipated in the atmosphere, and extensive formations are produced. So rapid is the 

 precipitation of carbonate of lime at the hot baths of St. Vignone, in Tuscany, that half a 

 foot of solid travertine is the annual product near their source. The hot waters of Hiera- 

 polis have been similarly productive. This city, now a site of desolate ruins, was 

 formerly one of the most flourishing in Asia Minor, and was resorted to for its thermal 



