stated in the last number of the Phil. Mag. that on a trial with Woolf's engines (who uses steam of high pressure) the effect, compared with other engines, is as 46255 to 19897, with the same quantity of fuel. You mention in your Annals of Philosophy, &c. that Count Rumford found it decrease with heat; but do not mention the rate. Is there any method of preventing the incrustation on the inside of steam engine boilers? What quantity of sugar may be obtained from a given quantity of starch?

I am, dear Sir, your most obedient,

Dundee, Oct. 17, 1815.

V. Royal Geological Society of Cornwall.

I. S.

Annual Report of the Council.-In presenting this Annual Report the Council cannot resist the pleasure of congratulating the Society upon the active zeal with which the various objects of its research have been pursued, and the eminent and unexampled success which has attended its labours: two years have not yet elapsed since its establishment, and yet how much has been effected! the cabinets are respectable, and in some departments even rich; the library is stored with many splendid and instructive works, in the various sciences connected with geology; and the laboratory has been furnished with all the apparatus necessary for the pursuit of analytical mineralogy; numerous interesting and original memoirs have been read, and a very considerable mass of materials has been collected for the construction of a Geological Map of the County; the miner too has been enlisted into our service, and has presented us with much valuable information of a practical nature, which, when digested and arranged, may tend to solve the important problems connected with the structure of our metalliferous veins, and at the same time he has enriched our portfolios by the addition of many beautiful plans and drawings.

While the objects of scientific research have been thus happily advanced, the interest of the miner has excited equal attention, and been promoted with equal zeal: the Economical Department of the collection is calculated to afford him much valuable instruction, it will teach him the characters and appearances of the different mineral substances employed in the various arts and marufactures of the kingdom, and enable him to recognize them whenever they may occur in his own districts, and thus open to him endless sources of profitable labour: the council therefore take this opportunity of soliciting the co-operation of the various mine agents, in order that they may more speedily enrich, and extend this most important part of the collection. Nor has the safety and lives of the miners been forgotten it is with infinite satisfaction that the council are enabled to state that the Tamping Bar composed of a metallic alloy, as suggested by Sir Rose Price, for the prevention of these fatal explosions which so frequently attend the use of iron instruments, through the humane and able exertions of

Mr. William Chinalls, has been so modified as to be free from all the former objections urged against its utility, and has accordingly been introduced into general use in many of the most extensive mines.

A valuable instrument also invented by Mr. Chinalls, called the Shifting Cartridge, well deserves the attention of the mine agent, its object being to deliver any given quantity of gunpowder into a hole bored in a rock for the purpose of blasting it, without that loss and hazard which attend the ordinary method of charging.

From this report the enlightened members of the community will be enabled to appreciate the value and extent of the labours of this society, they will discover the grand objects of the institution, and be induced, it is hoped, to co-operate in extending its views; by which the obscure art of mining will be improved, the health, comfort, and life of the laborious miner ensured, and the political resources and opulence of the county augmented.

Comparative View of the number of Members at the last and on the present Anniversary.-First anniversary, 109; withdrawn, 1; died, 3; elected this year, 36; total, 141.

The Treasurer reports that, although our expenses have been necessarily great, the Society is free from incumbrances, and has a considerable balance in its favour.

The following papers have been read this year :

1. On a Recent Formation of Sand-stone, which occurs on several Parts of the Northern Coasts of Cornwall. By John Ayrton Paris, M. D. F. L.S. &c.

2. An Account of the Granite Veins at Porth Just. By John Davy, M. D. &c.

3. Observations on the Gold found in the Stream Works of Ladoc. By Sir Christopher Hawkins, Bart.

4. Contributions towards a Knowledge of the Geological History of Wood Tin. By Ashurst Majendie, Esq.

5 An Account of the Relistian Mine, in Gwinear. By Joseph Carne, Esq.

6. A Sketch of the Geology of the Peninsula of the Lizard. By A. Majendie, Esq.

7. Answers to Geological Queries respecting Lodes. By Mr. John Davey, Associate.

8. Answers to Geological Queries. By Mr. John Stephens, Associate.

9. On the Granite Veins traversing Slate at Mousehole. By A. Majendie, Esq.

10. On the Geology of the Coast west of Mousehole, and on the Structure of the Scilly Islands. By A. Majendie, Esq.

11. Additional Notes to a Memoir on a recent Formation of Sand-stone. By John Ayrton Paris, M. D. &c.

12. Hints on the Geology of Cornwall.

Davy, Honorary Member of the Society.

By Sir Humphry

13. An Account of a Tamping Bar composed of a Metallic

Alloy; and of an Instrument termed the Shifting Cartridge. By Mr. W. Chinalls.

14. Observations on the Scilly Islands. By Henry Boase, Esq. 15. An Account of Silver Mines in general, and of those in Cornwall in particular. By Joseph Carne, Esq.

16. On the Lime-stone at Veryan. By Samuel Trist, Esq.

17. An Account of the Produce of the Copper Mines in Cornwall, Devonshire, Anglesey, North Wales, and Ireland, in Ore, Copper, and Money, for the Year ending the 30th of June, 1815, and of Tin raised in Cornwall, in the Year ending with Midsummer Coinage, 1815. By Joseph Carne, Esq.

At the Anniversary Meeting, October 10, 1815, the Right Honourable Lord De Dunstanville, &c. Vice Patron, in the Chair, the Report of the Council being read, it was resolved, That it be printed and circulated.-That the Museum of the Society be invested in the following Trustees: Lord De Dunstanville, Vice Patron; Lord Viscount Falmouth; Sir William Lemon, Bart.; Sir Rose Price, Bart.; Davies Giddy, Esq. M. P. President.

Lord De Dunstanville communicated to the Society, that Dr. Paris had been introduced to his Royal Highness the Prince Regent, the Patron, in order to present him with a Report of the Society, and that he had been most graciously received.

Thanks were voted to those Gentlemen who had contributed to the cabinet and library; to the authors of the different memoirs read before the Society; to Mr. Chinalls, and the other mine agents, who have exerted themselves in introducing the alloyed tamping bar; to John Ayrton Paris, M.D. for the zeal and ability with which he has conducted the Society, and for his Course of Lectures on Chemistry delivered before them last winter.

Sir Rose Price Bart. as the representative of those Gentlemen who had attended the Lectures, stated that he rose for the purpose of presenting Dr. Paris with a piece of plate, of 50 guineas value, as a small testimony of their esteem and regard.

It was further resolved, That a medal with an appropriate device be immediately struck, and presented to those miners who had contributed practical information to the Society, or who had by their exertions promoted its views.

VI. Prussic Acid.

A most important set of experiments on prussic acid has been lately made by M. Gay-Lussac. I shall lay the whole of them before my readers as soon as I can find room for their insertion. In the mean time I shall give a sketch of the results which he obtained, by way of notice, that I may satisfy the impatience of British chemists, and enable them to examine the curious substances which Gay-Lussac has discovered.

Prussic acid may be obtained by putting dry prussiate of mercury into a tubulated retort, pouring upon it muriatic acid in quantity not sufficient to decompose the whole prussiate, and applying a

moderate heat. Care must be taken that none of the muriatic acid passes over, and a tube filled with dry muriate of lime should be luted to the beak of the retort, in order to absorb all the moisture. The receiver should be surrounded with ice,

Prussic acid, thus prepared, is a colourless liquid, having a strong odour, and a taste at first cooling, then hot, and violently poisonous. Its specific gravity at 45° is 0.7058; at 64° it is 0.6969. It boils at 80°, and congeals at about 50. At that temperature it crystallizes regularly. The cold which it produces when converted into vapour, is sufficient, even in summer, to congeal it. The specific gravity of its vapour is 0.9360. This vapour was mixed with oxygen gas at 72°, and detonated in a Volta's eudiometer. 100 measures of the gas consumed 125 measures of oxygen; 100 measures of carbonic acid were formed, and there remained 50 measures of azotic gas. 100 of the oxygen went to the formation of carbonic acid, and 25 to that of water; hence the hydrogen present, if in the state of gas, would have amounted to 50 measures. It is evident from this analysis, that prussic acid is composed of

Prussic acid cannot be kept. It is decomposed spontaneously, and converted into prussiate of ammonia and a black matter composed of carbon and azote. Phosphorus and iodine may be sublimed in it without alteration. Sulphur combines with it. Potassium put into the vapour of prussic acid absorbs it, while a quantity of hydrogen is disengaged equal to half the volume of the prussic vapour. The potassium is converted into a yellow substance, soluble in water, and converted by this solution into prussiate of potash. From this result it is obvious, that prussic acid, like muriatic acid and hydriodic acid, is composed of a radicle combined with hydrogen. This radicle is obviously a compound of two atoms of carbon and one atom of azote. This radicle may be obtained in a separate state. Like chlorine and iodine it unites with many bodies; hence prussic acid, like muriatic and hydriodic acids, is composed of equal volumes of a radicle and hydrogen gas united together, without any diminution of bulk. Gay-Lussac has given the name of cyanogen to the radicle, and of hydrocyanic acid to what was formerly called prussic acid.

VII. Cyanogen.

Cyanogen is easily obtained by exposing what was formerly called prussiate of mercury, but which Gay-Lussac has shown to be a compound of cyanogen and mercury, to the heat of a lamp. The salt should be very dry. A gas comes over, which must be received over mercury. It is cyanogen gas. This gas has a very strong and peculiar odour. Water dissolves it, and acquires a sharp taste. It is inflammable, and burns with a blueish purple flame. Its specific gravity is 1.8064. It may be exposed to a very strong heat, without decomposition. Water dissolves 4 volumes of it, alcohol 23 volumes, and alcohol and oil of turpentine at least as much as water. It reddens infusion of litmus, and combines with the salifiable bases, and therefore possesses acid properties. Phosphorus, sulphur, and iodine, may be volatilized in it without change. Hydrogen has no action on it. Copper and gold do not combine with it, but iron partly decomposes it at a red heat. Potassium absorbs just as much of it in bulk as it separates of hydrogen from water.

For combustion it requires twice its bulk of oxygen gas. It detonates with great violence, and with a bluish flame.

100 measures of cyanogen thus burn and form 200 measures of carbonic acid gas, and leave 100 measures of azote. Cyanogen combines with several of the metals. It unites also with the alkalies and alkaline earths.

When these compounds are dissolved in water, the cyanogen is decomposed, and converted into carbonic acid, ammonia, and hydrocyanic acid; and what is curious, equal volumes of these three substances are formed, supposing them all in the gaseous state.

VIII. Chloro-cyanic Acid.

Berthollet observed long ago, that when chlorine was mixed with hydro-cyanic acid, the properties of this latter acid were altered. Its smell became much stronger, and it precipitated iron, not blue as before; but green. The new substance thus obtained was called oxy-prussic acid, because it was considered to be a compound of oxygen and prussic acid. Gay-Lussac has ascertained that it is a compound of equal volumes of chlorine and cyanogen, and on that account has given it the name of chloro-cyanic acid.

To obtain it, he passed a current of chlorine gas into hydro-cyanic acid, till that acid acquired the property of destroying the colour of a solution of indigo in sulphuric acid. By agitating the liquid with mercury he got rid of the excess of chlorine. The liquid was then distilled. He obtained a gas which was a mixture of chlorocyanic acid and carbonic acid; but chloro-cyanic acid is not an elastic fluid, but a liquid. He obtained it in that state by filling two thirds of a glass jar with mercury, and the other third with the hydro-cyanic acid, saturated with chlorine.. This jar was placed inverted over mercury, under the receiver of an air-pump. On producing a vacuum the mercury and liquid were driven out of