year ago at Liverpool, and have examined them after the many extreme hard gales they have stood, and I find them much less chafed, &c. in proportion than any sails in her on the old plan.

So perfectly convinced am I of the superior saving and safety of your mode of reefing, and making with horizontal cloths, that I have had a fore-sail on that plan made here, and I shall in every ship I am concerned in, not fail having my sails made on your plan.

I suspect few men who have experienced a severe gale of wind on a lee-shore, will for a moment hesitate in believing your mode of reefing, without starting tack or sheet, and strengthening the sails by making them with horizontal cloths, will be the means of saving lives and property.

Extract of a Letter from Captain Hornby, of the Birna, of Grimsby, to Mr, W. Gibson, Sail-maker of Hull.

December 1, 1806.

I approve of Captain Cowan's sails very much: the experience I had of them during our voyage to Davis's Straits, convinced me they answered every purpose set forth in the directions; and as long as I am enabled I shall not go to sea without them.

I am well aware there are men in most professions wedded to old customs and opinions, and vain would it be to point out to them their utility; but to me, the satisfaction I experienced in reefing courses without starting tack or sheet, or shaking the sail, will never be effaced from my memory: and let those seamen who

were

were never on a lee shore, or in a narrow passage, in a ship badly manned in a gale of wind, reflect that they are still liable to such cases, and then disapprove of it if they can.

These sails do not shake in hauling up to reef, therefore must last longer.

Description of an Improvement on Tide-Mills, to make them work as well at high and low Water as any other Time of Tide. By Mr. JOHN ISAAC HAWKINS.

Communicated by him in a Letter to the Editors.

GENTLEMEN,

I HEREWITH send you an account of another of the improvements exhibited in my Museum of Useful and Mechanical Inventions.

The improvement consists in having a reservoir to be filled by the tide at high water, through a canal fur nished with a valve sluice, so as to let the water pass into the reservoir, but not to go back again the same way. The content of this reservoir or upper pond is to be conveyed by the usual means over or under a water wheel, and then received by another reservoir or lower pond, where it is retained till the time of low water, when it opens another valve-sluice, and discharges itself into the river or sea from whence it was received.

Upon this principle a constant fall of water from the upper into the lower pond is obtained by means of the rising and falling of the tide, and that without requiring any person to attend it; for whenever the water is higher

in the river or sea than in the upper pond it will open the sluice and fill the pond; and whenever it is lower in the river or sea than in the lower pond, the weight of water in the latter will open the lower sluice.

The manner of making valve-sluices must be too well known to need description, since they are used on the low lands on the banks of most tide waters.

There are many situations on which this plan may be adopted with little expense: in places where the general level of the land is about half way between high and low water, nothing more would be necessary than to dig out the lower pond, and with the same earth make an embankment, which will form the upper.

The size of the ponds must of course depend on the degree of power wanted: if each will hold water enough to turn the wheel about ten hours, they will be sufficiently large, since the upper pond will be full at high water, and replenished again soon after the middle of the rising tide; and the lower pond will be empty at low water, and begin to be emptied again immediately after the middle of the falling tide.

The principle of this improvement may be added to those tide-mills already in use that work forwards and backwards.

Let two small ponds, an upper and a lower, be dug, each capable of holding water enough for turning the mill about two hours: these may be called auxiliary ponds, and the original one the main pond.

Let there be two channels for the water to go into the main pond, one under the water-wheel, and the other merely to fill the pond; and let there be a communication from the water-wheel channel to each of the auxiliary ponds, and also from these to the river or sea.

Then

Then might the motion of the water-wheel be always kept up with full force; for during the rising of the tide, and until within about an hour of high water, the current would be under the water-wheel and into the main pond as usual; but the force of the tide then slackening, the communication between the water-wheel channel and the main pond must be shut, and the current after passing the wheel be turned into the lower auxiliary; at the same time the tide must be admitted into the main pond through the other channel, and the upper auxiliary also filled.

By the time the lower pond is full, the tide will be running down strong enough to admit of the wheel being turned backwards, in the ordinary way, by the contents of the main pond passing back through the water-wheel channel. This will continue until about an hour before low water, when the contents of the upper auxiliary pond must be carried under the wheel, and then discharged into the river or sea, and the main and lower auxiliary ponds allowed to empty themselves.

Thus might all the advantages of the double-pond system be added to the tide-mills now in use with but little expense. They would, however, require more attention than if the mills were entirely upon that system, since it would be necessary to turn the water from one channel into another; whereas in the other case, the sluice-valves would be always worked by the pressure of the water.

I am, Gentlemen,

Yours, &c.

JOHN ISAAC HAWKINS.

An

An Account of the Application of the Gas from Coal to economical Purposes. By Mr. WILLIAM MURDOCH.

Communicated by the Right Hon. Sir JOSEPH BANKS, Bart. K. B. P. R. S.

From the PHILOSOPHICAL TRANSACTIONS of the ROYAL SOCIETY of London.

THE

HE facts and results intended to be communicated in this paper are founded upon observations made, during the present winter, at the cotton manufactory of Messrs. Philips and Lee at Manchester, where the light obtained by the combustion of the gas from coal is used upon a very large scale; the apparatus for its production and application having been prepared by me at the works of Messrs. Boulton, Watt, and Co. at Soho.

The whole of the rooms of this cotton mill, which is, I believe, the most extensive in the United Kingdom, as well as its counting-houses and store-rooms, and the adjacent dwelling-house of Mr. Lee, are lighted with the gas from coal. The total quantity of light used during the hours of burning, has been ascertained, by a comparison of shadows, to be about equal to the light which 2500 mould candles of six in the pound would give; each of the candles, with which the comparison was made, consuming at the rate of 4-10ths of an ounce (175 grains) of tallow per hour.

The quantity of light is necessarily liable to some variation, from the difficulty of adjusting all the flames, so as to be perfectly equal at all times; but the admirable precision and exactness with which the business of