[From Yn Lioar Manninagh Vol 3 pp65/74]
BY JOHN TODD, C.E.I
Mr. President, ladies and gentlemen, it is with mingled feelings that I have come here this afternoon. On the one hand I am afraid that I shall not be able to make your meeting so interesting as one would wish ; on the other hand, I rejoice to have this of opportunity of meeting you to explain, with what knowledge I have of the subject, the process of making salt, and give a short account of the borings that have been made by Craine Bros. In the year 1891 they leased certain grounds in the North of this Island and agreed to proceed forthwith to bore for coal to a depth of at least 300 feet. The site of the bore was selected at the Point of Ayre, which is the most northern point of the Island. The boring proved the boulder clay and sand to be 298 feet thick. After they were passed through, the bore entered the Triassic marl of the saliferous variety, and at a depth of 615 feet a brine run was reached.
On continuing the bore, it passed through 35 feet of salt. After the Triassic marls were found they indicated that coal would be very deep, and Craine Bros. were advised to put down another bore at Blue Point, which is nearly five miles to the west of the Point of Ayre, as shown on the map, Plate I. Operations were forthwith commenced to put down a second bore, and after passing through 171 feet of clay and sand with fragments of coal, it reached the new red sandstone, but there was some doubt as to its probable thickness, and this bore was discontinued until another was put down at Lhen Mooar, which is about one mile further to the west. This bore (No. 3) proved the existence of the carboniferous limestone, which belongs to an age much older than the coal measure. Its presence suggested that the new red sandstone was not thick at No. 2 bore. and operations were again commenced at this point. After penetrating 400 feet of new red, and 60 feet of conglomerate, the bore continued for a distance of 70 feet in rocks which have not been clearly identified, and then entered the carboniferous limestone.
It would seem that this bore only reached the point where the new red abuts unconformably upon the carboniferous limestone, as shewn on Section A, Plate II. After a somewhat painstaking inquiry as to the value of the results obtained, another bore (No. 4) was commenced on the lands of Knock-e-Dooney. It passed through 173 feet of drift, and has penetrated about 300 feet of new red sandstone You will notice that all the borings have been made near the foreshore, the object of this is to keep as great a distance as possible from the line of junction as shown on the map.i
Coming now to the question of finding coal, I suppose most of you will know that, in many places, the permian rocks rest on the coal measures ; but it is the opinion of a distinguished geologist that in the north of this Island they are more likely to rest on older rocks. On the other hand, Craine Bros. have been advised that the results attained do not justify such a conclusion, amid it would be foolish to abandon the work, so that in this case, as in all other scientific problems of the kind, there is a difference of opinion, and, under the circumstances, I think it better to remain silent in the matter. I may venture, however, to say that all seams of coal have a beginning and an end. There is no doubt coal is found in Cumberland extending for some miles under the sea, in the direction of the Point of Ayre, and the borings that have been referred to do not show that it ends before it reaches this Island. The red sandstone found in No. 2 and 4 bores has been identified as St. Bees sand-stone, and coal is found under it in the vicinity of Whitehaven.
Then, again, the limestone found at the bottom of No. 2 and No. 3 bores has been clearly identified as the carboniferous limestone which underlies the coal measures in Cumberland. The circumstances having been shortly narrated, I wish to direct your attention to Plate II., Section A, which shows how the rocks are supposed to abut at No. 2 bore, amid the comparative Section B, showing how the same rocks abut in the Cumberland district. Craine Bros. have been advised that the rocks shown on Section A. , as not clearly identified, belong to the coal measures. It would seem, however, that they have some resemblance to the lower carboniferous rocks, but whether that be so or not on the principle of reasoning from the known to the unknown, one cannot see why we should expect anything but a like occurrence of the Cumberland coal measures between Rue Point and the Point of Ayre. However, as silence becomes me most, I will leave you, as thoughtful, experienced men of affairs, to form your own judgment in this matter ; and propose to ask your attention for a short time to consider the result of the Point of Ayre boring, which has revealed the presence of a salt field with natural brine. It is probably caused by the sea water percolating down through the marls, and by the continuous motion kept up by constant pumping, the rock salt is eaten away in sufficient quantity to form fully saturated brine. The descendimig water causes it to rise nearly as far as the difference of specific gravity will permit. Saturated brine contains 26 per cent. of its weight in salt, and has a specific gravity of 1.204. Hence a column of such a solution of 500 feet will support one of pure water having a height of 600 feet. In other words, a column of fresh water of 600 feet will bring the brine within 100 feet of the surface. In our case the brine rises to a height of ~ feet from the surface, and the pump is at a depth of 160 feet. The difference between the two depths represents the head of water, or the power that keeps the brine in motion. It is delivered from the pump into a tank, where any earthy matter held in suspension is allowed to settle at the bottom. The clear solution is then run into the evaporatmg pan, which is 30 feet long by 12 wide and 18 inches deep. Heat is applied at one end by the combustion of coal, and the walls which serve to support the pan and distribute the heat conduct the products of combustion to the further extremity, where they escape into the chimney. On the surface of the heated brine, which for chemical purposes is kept at about 195 degrees Fahrenheit, minute cubical crystals speedily form. On the upper surface of these other small cubes of salt arrange themselves. This ultimately sinks to the bottom, where other small crystals unite with it, so that the shape frequently becomes completely cubical. For the production of table salt the boiling is carried on much more rapidly, and at a higher temperature than for chemical salt. The crystals are very minute, and adhere together by the solidification of the adhering brine, effected by exposure on heated flues. For fish-curing purposes the crystals are preferred very coarse in point of size, and to produce these the evaporating process is conducted at a low temperature. The analyses of the brine show that it is practically fully saturated, and the salt is chemically pure and of excellent quality, together with a hard grain, which is very desirable for fish-curing purposes. I shall now try to give an idea of the extent of this deposit. The area which contains it has not been thoroughly proved ; but, from the results of the borings that have been made, it is not unlikely that the salt will extend over an area of 200 acres, which will probably contain 8,000,000 tons of salt.
Nature is in everything wonderfully harmonious ; and one of the most evident dispensations of Providence is to make universal that which is most needful. We have a remarkable illustration of this in the fact that just as salt is one of the most widely distributed substances on the earth, so it is one of the most useful articles of commerce. This is shown by the production of salt from the British Isles, which amounts to about 2,000,000 tons per annum. The most of it is raised in England, there being no salt found in Scotland, and it is interesting to notice that the Point of Ayre salt field is the most convenient to the Scotch market. The yearly consumption of salt in that coumitry is over 100,000 tons, about 80 per cent. of which is supplied from Cheshire, and has to be conveyed some thirty miles by canal to Liverpool. It is there transhipped into larger vessels and conveyed, say, to Glasgow, which is considered the centre of Scotch commerce. From the geographical situation of the Island, and keeping the other circumstances in view, it would seem that salt could be conveyed as cheaply from the Point of Ayre to the Clyde as from Cheshire to the Mersey, so that in supplying the Scotch market there would be a saving of the cost of carriage between Liverpool and Glasgow.
Then as to the trade with other countries. The quantity of salt shipped from Liverpool to the East Indies in 1894 was 396,000 tons. A large quantity of this went by vessels trading to Glasgow
....plans etc TBD
see Boyd Dawkins