2

It contained no water, and must therefore be composed according to the formula, 2 Mg0+3 P,0,. This formula, the author shewed, could not be reconciled with the prevalent views of the constitution of phosphates, and the existence of this salt might therefore lead to some modification of these views.

The following Donations were presented :

The Journal of the Royal Agricultural Society of England. Vol V. Part 2.-By the Society.

Transactions of the Society for the Encouragement of Arts, Manufactures, and Commerce. Vol. LV.-By the Society. Memoirs and Proceedings of the Chemical Society. Part 11.-By the Society.

The Journal of Agriculture, and the Transactions of the Highland and Agricultural Society of Scotland, for March 1845.-By the Society.

Fifteenth Report of the Scarborough Philosophical Society, for the year 1844. By the Society.

Monday, 17th March 1845.

SIR GEORGE S. MACKENZIE Bart. in the Chair.

The following Commmunications were read :—

1. On the Improvement of Navigation in Tidal Rivers. By David Stevenson, Esq.

Three compartments are pointed out as existing in all rivers, when viewed in connection with the sea, possessing different characteristics, and requiring different classes of works for their improvement. These are, first, The “ sea proper," characterised by the presence of unimpaired tidal phenomena, and including all works connected with the improvement of bars. Second, The "tidal compartment of the river," characterised by the modified flow of the tide, produced by the inclination of the bed, and embracing works connected with the straightening, widening, or deepening, of the beds of rivers; the

formation of new cuts; the erection of walls for the guidance of tidal currents, and the shutting up of subsidiary channels. And the third compartment is the "river proper," which is characterised by the absence of all tidal influence, the improvement of which is generally effected by means of dams erected in the bed of the river, and forming stretches of canal communicating with each other by means of locks in the dams. The practical remarks are confined to the improvement of the tidal compartment only, which possesses sufficient importance to entitle it to form the subject of a distinct communication; the prosperity of the ports of London, Bristol, Newcastle, Glasgow, and many other places, being intimately connected with it.

The author shews, that, owing to the smallness of the rivers of this comparatively narrow country, they can be advantageously navigated only while their waters are deepened by the influx of the tide, and proposes, as the surest means of effecting improvement, such works as produce an increase in the duration of tidal influence.

Instances of the success of these works are given. The rise is the bed of the Tay from Newburgh to Perth (8.56 miles), in consequence of works that have been executed, has been reduced from four to two feet. The time occupied in the passage of the tidal wave between these places has been decreased fifty minutes, and the speed with which it travels increased 13 of a mile per hour. The duration of flood-tide at Perth has been increased fifty minutes, and the time during which the river at that place is uninfluenced by the tide, has been decreased forty-five minutes. It is also calculated that an additional quantity of sea water, amounting, on an average, to 760,560 tons, is propelled into, and again withdrawn from, that part of the river extending above Newburgh every tide. At the Rubble in Lancashire, similar benefits have resulted from similar operations; the tidal range at Preston having been increased between three and four feet, and the propagation of the tidal wave accelerated about forty minutes.

The following are the practical inferences which the author draws from the facts brought forward :

:

First, That owing to the comparatively contracted country from the drainage of which our rivers derive their supplies, it is chiefly from increased duration of tidal influence that we must expect improvement in tide navigation, the regulation of the fresh water stream being an operation of secondary importance, but not, on that account, to be overlooked.

Second, That the whole tidal phenomena of the navigation to be improved ought to be ascertained, in order that the engineer may be enabled to discover in what part of the river the most prejudicial retardations of the tidal wave, and obstructions of the current, take place.

Third, That, in tracing these retardations to the proper cause, and suggesting means for their removal, works should be adopted which do not injuriously abstract tidal water from the sea channels.

Fourth, That the works best suited for attaining the desired end consist chiefly in lowering the bed of the river, and removing all natural or artificial obstructions, and in erecting low rubble walls for the direction of the currents.

Fifth, That although general views of the nature of these operations may be given, the precise details of such works as shall be best suited to particular localities can, in the present state of our information, be determined only by Engineering experience. And,

Lastly, That, by the execution of works designed in accordance with these general views, very beneficial results have been, and may be, produced, for a comparatively small expenditure.

2. On the Solvent Action of Drainage Water on Soils. By John Wilson, Esq., F.G.S. Communicated by Dr Gregory.

The author, being resident for a time in East Lothian, in order to study the system of agriculture, it occurred to him that the very extensive and complete drainage must materially affect the soil by removing large quantities of its soluble ingredients.

He was disappointed, owing to an accident, in examining, quantitatively, the water which had been first collected for the purpose; but on examining, qualitatively, some that was collected after the drain had been running very copiously for 36 hours, he found it to contain 18.4 grains of soluble matter per gallon. This was chiefly the usual salts of lime and organic matter.

He examined the surface and subsoils of the field, and found them to contain, besides silica and alumina, iron, lime, and traces of magnesia, with organic matter. The iron in the surface soil was in the state of protoxide, but in the subsoil it was found peroxidised.

The author concludes that the drainage water carries off a very large quantity of the soluble matter of the soil, which he calculates as possibly amounting to 775 lbs. per acre in the year, a quantity

equivalent to a good dose of manure.

He recommends the adoption of some means to prevent this great loss, and promises to continue his researches, and bring forward more precise results.

The following Donations were presented :—

Anatomical and Pathological Observations. By John Goodsir,

F.R.S.E., and Harry D. S. Goodsir, M.W.S.-By the Authors. The American Journal of Science and Arts, conducted by Professor Silliman, for January 1845.-By the Editor.

Monday, 7th April 1845.

Sir T. M. BRISBANE, Bart., President, in the Chair. The following communications were read :

:

1. Observations on the Temperature of the Earth at Trevandrum, in Lat. 8° 30′ 32′′. By John Caldecott, Esq. Reduced, with some Remarks, by Professor Forbes.

The present notice is a sequel to one presented to the Royal Society on 1st May 1843, containing the results of Mr Caldecott's Observations on the Temperature of the Earth in India, made by means of thermometers sunk to depths of 3, 6, and 12 French feet, corresponding to those employed in the three stations near Edinburgh, of which the results are already before the Society.

The position of the instruments is mentioned in the former notice (Proceedings, vol. i. page 432).

A later note from Mr Caldecott, dated 10th August 1843, accompanies the detailed observations made upon the three thermometers four times a-day (every 6 hours) for the whole year, from July 1842 to July 1843, Sundays excepted.

The most remarkable circumstance connected with the observations, is the extraordinary excess uniformly observed of the earth temperature above the air temperature. The index error of the instruments is so large, as might have excited a suspicion of some inaccuracy in its determination, but for the known experience and skill of Mr Caldecott. I shall therefore quote what his letter says on this point. "The readings of the thermometers, as given in these tables [containing the observations at large], require a correction in order to reduce them to those of the standard thermometer. This correction, derived from a comparison of them with the standard,

made every two hours for rather more than a month, before they were put into the ground, is as follows:

This detail is even too minute to render a considerable mistake at all likely; we must therefore take the results as we find them, which are contained in the following table, where the numbers are all corrected, and compared with the mean temperature of the air, and the quantity of rain. It will be observed, that several of the observations of the warmer months have been lost, owing to the large index error having misled the maker as to the range which would be required, and consequently the spirit rose above the scale.

Abstract of Observations of Terrestrial Temperature at Trevandrum. Lat. 8° 30′ 32′′ N. Long. 5h 7m 59s E. of Greenwich.

With a view to deduce more carefully the results of this curious, and hitherto unique series of observations, I have had the observations for the year projected in the form of curves, on the same scale as those formerly submitted to the Society, of the earth tempera