12. The density of the feed-water should be kept as low as possible.

13. In constructing hydrometers, the quantity of salt left behind, for every 100 parts of water evaporated, should be registered, as upon this quantity must depend all calculations of effect in fuel.

14. Hydrometer-makers should not only engrave the temperature for which the instrument is fitted, and the scale of saltness, but also the specific gravity of the sea water, on which the scale was formed, and the proportion the muriate of soda bears in 100 parts of dry sea salt, in order to be able to make the necessary corrections for the varying saltness of the sea.

15. In order that sulphate and carbonate of lime should not be deposited, the degree of saltness should not exceed 25 parts for every 100 parts of water, or 60° of the hydrometer.

[Mr. HUNTINGTON

Mr. HUNTINGTON explained that as it had been necessary to omit the Tables in the reading of the Paper, he wished to say that they showed :

1. Results of Messrs. Maudslay and Field's experiments as to the relative temperatures of the brine and steam. 2. Results of Mr. Seaward's ditto ditto. 3. Analyses of different sea waters by Dr. Ure, Dr. Lardner, Dr. Murray, Schweitzer, and Laurens, and of common salt by Dr. Henry. 4. Experiments on the densities of different solutions. 5. Chemical analysis of salt. 6. Results of Gay-Lussac's experiments, to show that when the temperature of the water is raised, a greater quantity of common salt is required to saturate the solution. 7. Value of multiplier for pressures varying from 1 lb. to 20 lbs. per square inch above the atmosphere, in rule for determining the time required to acquire any concentration. 8. Results of Tredgold's experiments on the boiling points of solutions. 9. Results of experiments on the boiling points of solutions. 10. Sir G. Shuckburgh's barometric boiling points. 11. Dalton's pressures of steam near the atmospheric boiling point. 12. Correction of boiling points. 13. Capacities for heat of common salt, as determined by M. Gadolin. 14. Freezing points of different solutions, as determined by Mr. Griffith. 15. Capacity for heat of saline solutions. 16. Results of Watt's experiments with steam of a saturated solution. 17. Differences between the temperatures of the water and steam at several densities. 18. Temperatures of steam, at different pressures. 19 and 20. Showing the fuel required for a given capacity of boiler and pressure of steam. 21. Results of De Luc's experiments as to expansion of saturated solution of salt and of pure water. 22. Results of Dalton's and Gilpin's experiments on the expansion of pure water. 23. Results of experiments on the expansion of a saturated solution of salt. 24. Showing the loss of specific gravity by the expansion of pure and salt water. 25. For calculating corrections for the expansion of water and salt. 26. Showing graduations for salinometer scales. 27. Ditto corrections for the water. Ditto for the salt and temperature.

28.

Dr. RITTERBANDT said, it remained with the engineers to agree upon an instrument to determine the saltness of water. He had found that, in many ports of the United Kingdom, the instruments used for that purpose were different. If correct

results were to be arrived at, it was absolutely necessary that one and the same description of instrument should be adopted, so as to induce uniformity in the observations. He considered that it would be useful to have an indicator of brine saturation, out of the reach of the engineer; it would be safer in that position, and would undoubtedly lead to economy of fuel. As regarded the density of the water, supposing it to contain 3.5 per cent. of salt, if the engineer permitted eight times that amount, it would equal 28 per cent., which was too dense to be economical. Water would absorb a quantity of salt, which would raise its specific gravity to three times this amount, but at that degree it would be dangerous. There was very little salt really precipitated in the boilers; it was chiefly an incrustation, resembling salt somewhat in appearance, and consisting of carbonates of lime and magnesia, with small portions of sulphate of lime and of some common salt, if the density of the brine had been allowed to rise to its point of saturation.

Some time since he had used muriate of ammonia for preventing incrustation in marine and other boilers. It succeeded excellently with fresh water containing carbonate of lime. With salt water it did not absolutely prevent all incrustation, but it retarded its progress, and therefore the boilers did not require to be blown out so frequently. By the use of muriate of ammonia no great amount of incrustation was formed on the voyage, and on arrival in port the boiler was easily cleaned out.

In 1847, the Admiralty ordered some experiments to be tried at Portsmouth, to test the merits of the application. The practice had been to blow off when the hydrometer indicated 18° and 19°. By the use of muriate of ammonia, it was found that there was no incrustation, or deposit, even when the water had arrived at 60° hydrometer, or above three times the ordinary point of blowing off. In fact, the necessity of blowing off at 19° or 20° did not arise from the accumulation of salt in the water at this density, but from the deposition of the carbonates of lime and magnesia, held in solution by the free carbonic acid, which was expelled when arriving at this point, and this, the addition of muriate of ammonia completely prevented, so that the concentration of the water could be carried up to the point of saturation by the salt, but could not be carried beyond it, for then salt itself was deposited.

May 3, 1853.

JAMES MEADOWS RENDEL, President,

in the Chair.

The following Candidates were balloted for and duly elected : -Herbert Francis Mackworth, as a Member; James Forbes, James Needham Gildea, Henry Palfrey Stephenson, and Lieutenant Henry Whatley Tyler, R.E., as Associates.

No. 895. "Description of the Chesil Bank, with remarks upon its origin, the causes which have contributed to its formation, and upon the movement of Shingle generally."

COODE, M. Inst. C.E.

By JOHN

THERE are few subjects of greater professional interest, than the accumulation and travel of shingle, since the very existence of many harbours depends, in a great degree, upon a correct understanding and judicious application of the laws which govern its movement; and without a knowledge of these, it is impossible to devise such measures as may with confidence be adopted, either to asssist its progress, direct its course, or to remove accumulations that may have taken place. Such being the case, it is somewhat surprising, that conflicting opinions should be found to exist, and that there should be an unusual absence of well-ascertained facts bearing upon the subject.

The Chesil Bank is one of the most remarkable features of the south coast of England. It is perhaps the most extraordinary, and at the same time the most extensive, accumulation of shingle, to be met with in this country; there is reason to hope, therefore, that a description of it may not be devoid of interest, to the Members of this Institution.

It is proposed to give, in the first place, a description of the Bank as it now stands, with a notice of its past condition, according to the best authorities; and secondly, to point out the sources from which the shingle has been derived, with some

The discussion upon this Paper was extended over a portion of two evenings, but an abstract of the whole is given consecutively.

remarks upon the causes contributing to the formation of the Bank, and the conditions and circumstances which affect the movement of shingle generally.

It should further be premised that, with the execption of Fig. 1, which is compiled from authentic sources, the plans, sections, &c., on Plate 2, have been constructed from a great number of careful observations made by, and under the directions of the Author, for the special purpose of ascertaining and recording the facts connected with this great work of nature in its present state.

Fig. 1 is a general chart of the West Bay, showing the geological features of the coast line.

Fig. 2. Plan and longitudinal section of the Chesil Bank, showing "The Fleet," Portland, &c.

Fig. 3. Transverse sections of the Bank, at three points, as marked by the letters AFC on the plan and longitudinal section, Fig. 2. These sections represent its ordinary summer condition, and extend to 600 feet, seaward, from low-water mark.

Fig. 4. A section of the west side of the Bank, near "Chesil," showing the profile of the Bank after the gale of 27th December, 1852, and its close correspondence with a true parabola.

Fig. 5, is a plan, with contour lines, of a gully or "can," caused by the water passing through the Bank during heavy south-west gales.

Fig. 6, shows one of the peculiar boats, called "lerrets," used by the fishermen on the Chesil Bank.

The Chesil Bank is a vast mound of shingle, in the form of a narrow isthmus, lying upon the western seaboard of Dorsetshire, between Abbotsbury and Portland; its general direction, or bearing is south-east, and its length is 10 miles.

Commencing at Abbotsbury Castle (to the westward of which the shingle slopes down from the low cliffs, as in the case of an ordinary beach) the Bank skirts along the margin of the meadows, for half a mile, when it meets "The Fleet" or "Backwater," a shallow estuary varying from a quarter to half a mile in width; it then runs parallel to the general line of the main land as far as Wyke, a distance of eight miles; from this point, the Bank takes a more southerly direction, until it joins the Peninsula, or what is more commonly called the Island, of [1852-53.]

2 M