About thirty years since a brine spring was discovered at Birtley colliery 76 fathoms below the surface, in driving a water level through a slip of 4 fathoms throw. The spring being found to produce 26400 gallons of water in twenty-four hours, extensive salt works were erected on the spot, which are still carried on with success. Within 50 or 60 yards north of the slip, from which the spring issues, the Birtley dyke before mentioned crosses the strata from east to west, casting up the coal measures on the northern side 99 fathoms; and the slip having a south-eastern direction probably meets the dyke and is a branch from it. The water level is driven in a bed of blue shale containing ironstone in beds and in nodules. The analysis of the water by Mr. G. Woods is as follows.[1]
| Contents in | 1000 grains of water. | |||
| Dry muriate of soda | 87 | |||
| Dry muriate of lime | 43 | |||
| Muriate of magnesia | 1 | |||
| Carbonate of lime | ||||
| Carbonate of iron | ||||
| Silica | ||||
| ── | ||||
| 131 | grains | |||
| A little carbonic acid gas. |
Before the publication of Camden's Britannia in 1607, a brine
spring had been observed to issue from the rocky bed of the Wear
at Salt water Haugh near Butterby; for in that work it is first
mentioned. In 1684, Mr. Hugh Todd drew up an account of this
- ↑ The carbonates, small as is their proportion, are sufficient to make the water appear turbid, when viewed in the large reservoirs at Birtley. They are very readily thrown down by the addition of quick-lime, and this method of purifying the solution is always pursued in that salt-work. The brine leaves no incrustation upon the evaporating pans.
