Downloaded from http://pygs.lyellcollection.org/ at Rice University on July 24, 2015 401 ON THE CIRCULATION OF SALT AND ITS BEARING ON GEOLOGICAL PROBLEMS, MORE PARTICULARLY THAT OF THE GEOLOGICAL AGE OF THE EARTH. BY WILLIAM ACKROYD, F.I.C., F.C.S., PUBLIC ANALYST FOR HALIFAX. (Read April 2bth, 1901.) INTRODUCTION. Common Salt or Sodium Chloride is probably the most widely distributed of all sodium compounds, as it is one of the most soluble. During our investigation of the underground waters of N.W. York• shire, a fruitful aspect of its solubility was presented to us in the disappearance of three tons of salt in a runnel of 19,800 gallons per day. It went down the Smelt Mill Water Sink and reappeared after 10 days at Malham Cove, where the amount of combined chlorine in the water suddenly rose from one up to six parts per 100,000, and in the course of another eight days slowly fell to the normal unit.* We had a similar experience at Clapham. It is apparent, therefore, that any salt in the soil, or in underground channels is carried quickly away by the water, and such soil or underground channels would be thenceforth free from the compound, unless in the course of disintegration fresh quantities were exposed for solution. This, however, is so slow a process that it quite fails to account for the enormous amounts of chloride annually conveyed by rivers to the sea. The position is, perhaps, better seen in the following statement of fact:—The Widdop Reservoir, belonging to the Halifax Corpora• tion, contains some 640*5 millions of gallons of water, and I estimate it to contain 55 tons of salt. The 2,000 odd acres of gathering ground is moorland on Millstone Grit for the most part with a little of the Yoredale Rocks. Needless to say it is a saltless area, yet the 55 tons of salt is renewed probably more than once a year in the course of filling up to replace the Corporate demands on the reservoir. The chlorides come down in the rain-water. We may take it then, as a working hypothesis, that rain has brought down the salt whicli has been derived from the sea, and that to the sea it quickly returns. *Proc. Yorks. Geol. and Polytec. Soc, Vol. XIV. Ft. I., p. 17. I Downloaded from http://pygs.lyellcollection.org/ at Rice University on July 24, 2015 402 ACKROYD : ON THE CIRCULATION OF SALT. It will be convenient to speak of this salt as " sea-salt," in contra• distinction to such as may be derived from the earth by solvent denu• dation, which will be referred to as " earth-salt," and the proportionate amount of the sodium compound will be indicated in this paper by the chlorine figure. CIRCULATION OF SEA-SALT. The conditions obtaining in the Widdop area are of more than ordinary scientific interest, and I have made an experimental in• vestigation of them during the winter 1900-1, which has been com• municated to the Chemical Society of London.* From. November 12th to February 18th weekly chlorine determinations were made of the reservoir water, of the water in a rain-gauge kept close by, and of rain-gauge water on four other gathering grounds some miles to the east of Widdop, viz., Walshaw Dean, Midgley, Warley, and Ovenden Moors, besides daily tests of rain-gauge water from Belle Vue, in the town of Halifax. The area under investigation, with its position in England and the relative positions of the rain-gauges, are given in Plate LXVI. The results of the weekly tests are shown in the following table CHLORINE, PARTS PER 100,000 IN RAIN-GAUGE WATER. AViddop AViddop. Walshaw Midgley Warley Ovenden Height above Reservoir. Dean. Moor. Moor. Moor. sea level. 1,050 ft. 1,380 ft. 1,350 ft. 1,325 ft. 1,375 ft. November 12 1-2 0-8 0-3 1-1 J-2 1-3 19 — 11 0-7 0-7 0 45 0-5 26 1-0 10 0-65 ir> 0-6 0-8 December 3 1-0 0-5 ! 1 -05 0-7 0-9 0-7 10 — 0-2 : 0-6 0-0 0-ii 0-5 17 11 0-2 0-8 0-7 0-8 0-7 24 115 3-3 2 •.">,•"> 31 21 2 45 31 11 11 ! 09 1-6 11 0-9 January 7 1-2 1-2 i — 0-55 21 1-8 14 1-3 6-5 1 2-75 2-55 2 4 3 1 21 1-2S 0-85 i 11 10 1-1 0 75 28 1 -25 1-75 i l(i 1-8 1-9 1-4 February 4 (?) 1-4 0-8 ! l-O 2-7 1-2 1-4 11 1-2 1 *75 ! io 245 2-2 1-8 18 1-3 — —. Average 1-188 1-50 — 1 - — * Trans. Chem. Hoc, Vol. 79, p. 673. Downloaded from http://pygs.lyellcollection.org/ at Rice University on July 24, 2015 Downloaded from http://pygs.lyellcollection.org/ at Rice University on July 24, 2015 ACKBOYD : OX THE CIRCULATION OF SALT. 403 The reservoir water was fairly constant with an average of 1/188 parts of chlorine per 100,000. This figure will be greater than that of the annual average rainfall on account of evaporation, and if we deduct 10 per cent, it would still be equivalent to a fall of 172 lbs. of common salt per acre with the 1899 rainfall of 43-17 in. The rain-gauge figures fluctuated wildly. Widdop rain-gauge water reached 3"3 per 100,000 during a December week when a violent storm was blowing from the Irish Sea about 40 miles away, and on another occasion it got up to C-5. The average for the 14 weeks of observation was l-50. That the winter average should be in excess of the yearly average is in keeping with the results obtained by other observers, and gives some idea of the activity of salt circu• lation during the stormy part of the year when gales are prevalent from the sea. The abnormally high figures obtained at Widdop synchronised with similarly high figures for the other gathering grounds ; this is well seen in the plotted curves for the rain-gauge results. (Plate LXVIL, fig. 2.) Observations on chlorine in rain-water have been made at Ciren• cester since 1870 by Professors Church, Prevost, and Kinch.* An abnormal amount of chlorine has almost always been traced by them to salt spray from the Bristol Channel, 35 miles away. On different occasions immediately after a storm from the S.W. crystals of common salt have been found on the College windows facing west. The same kind of evidence has been furnished to me by Mr. J. H. Howarth respecting Malham; concerning Leeds by Mr. J. E. Bedford, and Mr. J. Denison calls my attention to the following references : " The winds from the South-West have sometimes blown so strong that the pieces of cloth on the tenters in several parts of Halifax parish have been charged with a considerable number of saline particles brought from the sea, t and further, " Sea-salts have been found deposited on the windows in West Park and York Place. Harrogate, thus giving practical evidence of the presence of the sea-breeze."| * Trans. Chem. Soc, Vol. 77, p. 1271. t Watson's History of Halifax, 1775, p. 5. + The Use and Abuse of Harrogate Mineral Waters, by Arthur Roberts, p. 32. Downloaded from http://pygs.lyellcollection.org/ at Rice University on July 24, 2015 404 ACKROYD : ON THE CIRCULATION OF SALT. The following is a synopsis of results up to date, the chlorides in the rainfall being calculated into annual downfall of salt per unit area:— Distance Place. from Deposit of NaCl per the Sea. acre per year. Cirencester .. 35 miles | 36 lbs. (average of 26 Church, Prevost, and years) i Kinch* Rothamsted .. 24'59 lbs. (average 6 | Lawes, Gilbert, and years) 1 Warrington f Perugia 75 miles 37-8 lbs Belluccit George Town, 186 lbs i Harrison t Demerara Widdop 40 miles 172 lbs. Ackrovd As to the particular nature of this salt circulation, we may suppose (1) that salt spray from the sea is carried to the land to distances varying with the force of the wind ; (2) that when the salt is dried by evaporation it is carried further inland with the dust; and (3) that rains dissolve it and bring it down to the rivers by which it is carried back to the sea. Of the carrying of the salt spray, abundant evidence, as I have shown, has been obtained in times of storm, and of the presence of sodium in dust at all times the spectroscope yields never-failing proof, while in the examination of rain-water I have found the highest chlorine contents in light rainfalls. The full extent inland of salt circulation has yet to be determined. It may not be entirely limited by mountain chains barring the direction of prevalent sea-winds, as finely-divided sea spray may possibly be carried nearly as far as the dust of Krakatoa. This much, however, we know, that the farther one gets inland and the less the chlorine figure becomes for rain-water. Angus Smith has published some averages for rainj in terms of hydrochloric acid per million. I have converted his figures to parts of chlorine per 100,000 of rain-water, and arranged them as follows in proof of this diminishing distribution : Ireland, Valentia .