I have now concluded the most important of the geological observations I had to make upon the Coal-field, and it remains only to give some account of the mineral springs that occur within its limits, and of the deleterious gases to which the mines are subject.
The mineral springs have been found either bursting out at the surface, or have been discovered in the shafts of mines, and in the dykes that intersect the strata. Those impregnated with common salt have been noticed in the pits at Walker, Wall's end, and Percy main, and in most of the deep mines between Newcastle and Shields: on the Wear they have been found at Birtley and Lumley-thick, and appear rising to the day at Ouston 1 mile west of Birtley, and at Butterby near Durham.
The spring at Walker issues into a deserted shaft from a bed of slate-clay at the depth of 55 fathoms; but being dammed up rises 33 fathoms higher to within 22 fathoms of the surface, and 15 fathoms of the level of the Tyne. It is pumped from a reservoir in the pit for the manufacture of soda, the salt obtained in the intermediate process being exempted by an Act of Parliament from the salt duty. The following is the analysis of this water by Mr. G. Woods.
| Contents in | 1000 grains of water. | |||
| Dry muriate of soda | 82 | |||
| Dry muriate of lime | 10 | |||
| Muriate of magnesia | 1 | |||
| Carbonate of lime | ||||
| Carbonate of iron | ||||
| Silica | ||||
| ── | ||||
| 43 | grains | |||
| A little carbonic acid gas. |
