140 Professor J. D. Forbes on the 



subject, however, to the variation formerly mentioned, that when the 

 brine is actively withdrawn by pumps, for the manufacture of salt, 

 the periods lengthen. I have no additional observations of import- 

 ance to offer on this spring, beyond the remarkable fact of the con- 

 tinuity of these variations, surely the more remarkable when we 

 recollect that the spring is entirely artificial, rising through an 

 Artesian bore 312 Bavarian feet deep. 



Much greater changes have taken place in the Schonborn Quelle, 

 briefly referred to in my former paper as having a depth of 550 

 Bavarian feet, as overflowing once in seven or eight minutes, and 

 yielding a feeble supply of weak brine, containing only one and a 

 half per cent, of salt. The boring process has been carried on, 

 though slowly, nearly ever since, and it is at present one of the 

 deepest Artesian bores ever made, being, at the time of my visits, 

 1878 feet. The bore passes first through Bunter Sandstein 

 (which forms the bed of the valley, the surrounding heights being 

 capped by muschel kalk and keuper), to a depth of 1240 feet; the 

 only spring met with in that space being the small salt spring which 

 existed in 1838, which occurred at a depth of 222 feet, with a tem- 

 perature of 8° Beaumur ; it yielded only 6 cubic feet per minute, 

 with 1^ per cent, of salt. On piercing the sandstone from between it 

 and the gres vosgien rose a powerful spring, containing 2^ per 

 cent, of salt, of a temperature of 15° Beaumur, or 66° Fahr., and 

 yielding from 93 to 100 cubic feet of water per minute, and proba- 

 bly quite as much carbonic acid gas. These fluids were driven up 

 the shaft with enormous force by subterranean pressure. 



Not satisfied with this considerable success, the intelligent in- 

 spector, Mr Knorr, continued the laborious and expensive work 

 of boring, in the confident hope of reaching, if not the bed of 

 salt, at least the spring of stronger brine. At 1590 feet the upper 

 limit of the zechstein or magnesian limestone was reached, and at 

 1680 feet a source of carbonic acid gas appeared, which increased 

 the height to which the water could be driven up. At last, at 1740 

 feet, the limits of the rock salt formation was attained, the boring 

 irons bringing up saliferous clay, mixed with gypsum and anhydrite, 

 which continued down to the depth of 1878 feet, and which is capa- 

 ble of impregnating the salt water to saturation, coming up charged 

 with between 27 and 28 per cent, of salt. It is to be observed, 

 however, that it is only that portion of the spring rising at 1240 

 feet which can descend to the bottom and then rise up in this state 

 of saturation. The greater part retains its old per-centage of 2^. 

 It is therefore of urgent consequence to continue the bore until a 

 spring has been reached at a lower level than the salt, and of sufficient 

 power to rise through it to the surface, and in that way alone can 

 this mineral treasure be made available for use ; and as the thickness 

 of the rock salt formation is supposed to be 700 or 800 feet, it may 

 be long yet before this object is obtained. At present, if I under- 



