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During the passage round to Portsmouth, the speed of the vessel was purposely checked, by blowing off steam, to see the effect on the sillomêtre. The speed, as shown by the sillomêtre was gradually reduced from 8 miles per hour to 4, at which point it stood steady. On the order being given for full speed, the sillomêtre showed a gradual increase of speed, till it came to 8 miles per hour, as before.

On the return voyage, from Portsmouth to Woolwich, the distance performed

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(During the voyage from Woolwich to Portsmouth.)

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13 25 55-85 Fathom Channel; Cant Shoal; depth of water, about

h. m.

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3 25

13.15 55 7

16 feet

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It will be seen from the above observations, that at Woolwich the thermometer stood at 12°; as we got into deeper water, it rose to 13:55°; as we approached the Cant Shoal, it fell very rapidly to 13-15°; when off Dover, it had risen to 16°; 7 miles to the eastward of the Owers, it rose to 16.15°; and in Portsmouth Harbour, it fell to 14.2°.

From which it appears, that the marine thermometer, in its variations, followed the inequalities of the bottom of the sea, so far as these inequalities could be ascertained from the heaving of the lead, or from the information of the pilot; that is, on the approach to shoal water, the thermometer fell, and on the approach to deep water, it rose.

It may be inferred, that the marine thermometer would indicate the approach to rocks and icebergs, from the influence these bodies are known to have on the temperature of the sea, for a considerable distance.

III.-Trials with the Steam Thermometer.

(During the passage from Woolwich to Portsmouth.)

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V. Trials with the Steam Thermometer in the Medway.

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The observations here taken show how every variation in the temperature of the steam in the boilers is indicated by the steam thermometer of M. Clement. Thus, when the vessel was stopped, the temperature of the steam was 111.5 (centigrade); on getting under way, it lowered to 100°-3; going easy, it rose to 1100-9: going on again, it lowered to 110° 1; going easy again, it rose to 11095; going on at full speed, it gradually lowered to 106.9.

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The following remarks may serve to shew the uses for which these instruments are available.

The dial of the marine thermometer is on deck, and shows by inspection merely, the approach to shoal and deep water, also, (as it is inferred,) the approach to land, rocks, and ice-bergs.

The steam thermometer is so placed, that the officer on deck observes the degree of temperature (and pressure) of the steam in the boilers, so that, if from any cause, the temperature of the steam in the boilers becomes higher or lower than it should be, it immediately becomes known; and, in high-pressure engines more especially, the approach to such a degree of temperature and pressure as may be dangerous is easily observed.

The sillomêtre has also a dial upon deck, which constantly shows the number of miles per hour that the vessel is going; consequently, it is easy to discover, under all circumstances, what is the best trim of the vessel, and the most advantageous quantity and distribution of the sails, for obtaining the greatest speed. As the sillomêtre shows immediately, the effect which every alteration in the sails or trim of the ship has on its velocity, it follows also, that ships fitted with the sillomêtre can constantly maintain the speed that may have been agreed upon, and so keep company together, and maintain the same relative position, though, from the darkness of the night, or thickness of the weather, they cannot see each other.

To ascertain the distance run after any number of hours, it is simply to take the number of minutes one of the watches of the sillomêtre has gained over the other, and to multiply that number by 6, there results the distance run in miles.

The instruments of Monsr. Clément, fitted on board the "Lightning," appear to be well and securely placed; nor does there appear to be any danger of their being deranged.

When once fitted a simple inspection is all that is necessary to obtain the results.

JOSEPH LARGE, Foreman of Woolwich Dockyard.

In consequence of this favourable report on M. Clément's own instruments in the "Lightning," the Admiralty directed a set to be made by Mr. Carey; these English instruments have just been fitted to the "Blazer," Captain Washington, whose report we hope to be able to give in our next number.

CAPTAIN NORTON'S CONCUSSION SHELLS.

DEUXIEME SERIE, TOME QUATRIEME, NUMERO 10 OCTOBRE, 1833. "Ce serait une découverte bien importante dans l'art de la guerre, que celle d'une methode infaillible et non dangerouse, de faire eclater les Projectiles creux à l'instant de leur chóe contre le but. Malgre tout ce qui a été proposé par les Auteurs (Voyez Segemenowitz, Macdonald, Legris, Montgery, etc.) et tout ce qui a été avancé par les feuilles publiques cette invention est encore á faire, elle aura probablement les corps fulminants pour base.—From Le Journal des Sciences Militaires."

R. N. C. Sept. 11th., 8841.

My dear Sir. The object you propose to attain by your Percussion Shell, is very desirable, and if such a Spherical Shell can be prepared and used with safety, it will be one of the most important improvements made in Gunnery

* Concussion.

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