In the last volume of the Annual Register, we gave a historical view of the progress of the different sciences, from the first dawnings of philosophy to the present times. This view, though much shorter than we could have wished, was as extensive as consisted with our limits. Our object, at present, is to lay before our readers a view of the additions which have been made to the different sciences during the course of the year 1809-10. Though we shall confine ourselves as nearly as possible to that period, it will not be in our power to do so entirely; for we cannot always make a discovery intelligible to our readers, without laying before them the circumstances, or the train of investigation, that led to it, which may sometimes oblige us to go farther back than the period of which we professedly treat. We must warn our readers, too, that the present period is unfriendly to science of almost every description. The awful contest in which Europe is engaged has a tendency to withdraw the attention of men from the peaceful pursuits of science, and to fix them upon political considerations. The iron hand of despotism has crushed some of the finest regions of Europe, and banished from them even the

freedom of scientific investigation. Some of the most illustrious ornaments of the sciences on the continent have been reduced to abject poverty. verty. Even in France, the country which has been the instrument em ployed in crushing the other nations of Europe, the trade and manufac tures have been nearly annihilated, and learning, as a necessary consequence, has been discouraged and has declined. Britain, favoured by its insular situation, by its naval superiority, and by the energy of its government, has hitherto escaped the storm which has laid waste almost every other part of Europe. It is in Britain, accordingly, that the greatest scientific discoveries have been made.

Whoever has paid any attention to the history of the sciences, must be aware that there are certain æras when the general attention of scientific men is drawn to peculiar sciences almost exclusively. Thus, for example, during the greatest part of the seventeenth century, mathematics almost solely occupied the atten tion of scientific men. About the middle of the eighteenth century, electricity became the fashionable study, and every person of a liberal edu cation was under the necessity of ma

king himself acquainted with that science. For some years past, che mistry has become the prominent object of investigation, and has, in some measure, supplanted the other sciences. It is in chemistry, therefore, that the greatest number of discoveries are to be expected: it occupies the fore-ground of the picture; we shall therefore commence our history with that science.

1. The most splendid discoveries in chemistry which have been made in modern times, owe their existence to an apparatus invented by Volta, an Italian philosopher of great eminence, and first described by him in the Philosophical Transactions for 1800. He found, that when plates of copper, plates of zinc, and wet cloths were piled above each other in regular order, placing the copper lowest, then the zinc, then the wet cloth, then copper again, then zinc, then the wet cloth, and always observing the same order till 40 or 50 pairs of the plates, with wet cloths between them, were raised into a pile, then if the finger of one hand be brought in contact with the bottom of the pile, and the finger of the other hand with the top of the pile, an electrical shock is felt at the instant of contact. If a wire be made to pass from the bottom to the top, so as to complete the circuit, a current of electricity passes through the pile, and continues to pass for a considerable time this pile got the name of the Galvanic Pile, because some discoveries of Galvani gave birth to the investiga tions which led to the discovery of it. The galvanic apparatus soon under went considerable improvements. In stead of the pile, Mr Cruickshanks substituted a trough of wood, into which each pair of plates, previously soldered together, was cemented.

Between each pair of plates there was a cell, these cells were filled with a liquid, and the trough was fit for action. Various liquids were used, but the most efficacious was found to be a very weak nitric acid. Very considerable improvements were gradually introduced into the trough, both in the size and shape, and position of the plates. The latest and most approved form is this: The trough is made of stone-ware, and is divided into cells by diaphragms of stone-ware, about three quarters of an inch distant from each other. The plates are cut square, having a slip attached to the upper part of each, about an inch high, and thicker than the rest. These slips only are soldered together, so that there is a certain distance between the two plates at every part, except where they are soldered. Each pair is let down into the trough, so that there is a diaphragm of stoneware between the plates. The liquid is then poured in, and the trough is fit for action.

Almost all the discoveries in chemistry, which have resulted from the use of the galvanic trough, have been made in England. Messrs Nicholson and Carlisle discovered, that if a wire of platinum or gold be attached to the extremity of the trough at which the zinc plate is, (which we shall call the zinc end,) and a similar wire to the copper end, if these two wires be introduced into a glass of water, and placed within a small distance of each other, the water will be decomposed, the oxygen gas being separated from the wire attached to the zinc end, which is the positive end, and the hydrogen gas from the wire attached to the negative or copper end. By the subsequent experiments of Cruickshanks, Wollaston, Davy, &c. it was found that other substances

besides water, for example, nitric acid, sulphuric acid, ammonia, metallic oxides, &c.-were decomposed by the same energy, and that the power of decomposing depended upon the size of the trough.

But Mr Davy is the person to whom we are indebted for the most important discoveries respecting the action of the galvanic trough. By a most ingenious and satisfactory set of experiments, he succeeded in demonstrating that galvanism has the property of decomposing all compound bodies, provided it be sufficiently strong, that oxygen and acids always separate at the wire in contact with the positive end of the trough, while hydrogen, alkalies, earths, and metals, accumulate round the negative pole. Galvanism then, or electricity, is capable of destroying chemical affinity, however powerful, and of producing repulsion and consequent separation between particles of matter, however intimately combined. From this curious and unex. pected law, Mr Davy drew, as an inference, that when bodies unite chemically, they are in opposite states of electricity, the one negative, the other positive; and that when they are brought to the same state they no longer remain united, but repel and immediately separate from each other, 2. It had long been the opinion of chemists, that the fixed alkalies are compounds, but all attempts to decompose them had entirely failed. It occurred to Mr Davy, that the gal. vanic battery, which he had found so powerful an instrument of decomposition, might be successfully used to separate the constituents of these bodies from each other, Various unsuccessful trials were made; at last he found that, when a piece of potash is left exposed to the air for an in

stant or two, it becomes sufficiently moist on the surface to conduct electricity. If, in this state, it be placed upon a disc of platinum, connected with the negative extremity of the galvanic trough, and a platinum wire from the positive extremity of the trough be made to touch it, gas is evolved, and small metallic globules, similar to globules of mercury, make their appearance. New experiments informed him, that the gas evolved was oxygen, and that the potash, by the galvanic energy, had been decomposed into oxygen and the metallic substance. Óne hundred pair of plates of 6 inches square form a gal vanic battery sufficiently powerful to decompose potash. Soda is like wise decomposed by the same means, but it requires a more powerful battery. Thus Mr Davy ascertained that potash and soda are metallic oxides. To the metals which constitute their basis he gave the names of potassium and sodium.

These bodies differ exceedingly from all the metals with which we were previously acquainted. By the galvanic battery, they could only be obtained in small globules; but Thenard and Guy Lussac, two French chemists, discovered a me thod of obtaining them in consider. able quantity. Into a bent gun. barrel, previously coated on the outside with clay, a quantity of iron turnings are introduced; the gunbarrel is then placed in a furnace in such a manner that the iron turnings can be raised to a very high tempera ture. To one end of the gun-barrel a bent glass tube is luted, containing some mercury, in order effectually to exclude the air. To the other extremity an iron stopper is ground, containing about two ounces of potash, previously exposed to a red

heat. When the iron turnings are raised to a white heat, the potash is melted by means of a chauffer, and suffered to pass slowly through the turnings. It is decomposed; hydrogen gas rushes out of the glass tube in abundance, and after the process is at an end, the potassium is found towards the extremity of the gun-barrel to which the glass tube is luted. This process has not hitherto succeeded in furnishing sodi

um.

of

3. Potassium possesses the following properties, as ascertained by Mr Davy. Its colour is white like that mercury. At the temperature of 100° Fahrenheit, it is as fluid as mercury; at 50° it is a soft and malleable solid; while at 32° it is hard, brittle, and crystallized in facets. It is much lighter than any other metallic body known, swimming in all liquids, even the lightest oils. Mr Davy estimated its specific gravity at 0.7 70. Its affinity for oxygen is so great, that it cannot be left exposed to the atmosphere without instantly changing its state. The surface is immediately covered with a coat of potash, which absorbs water; this water is decomposed, new potash formed, and in a very short time the whole mass is converted into liquid potash. When thrown upon water, it decomposes that liquid with great rapidity, hydrogen gas is evolved, which holds a little of the potassium in solution, and, in consequence takes fire as soon as it comes in contact with the air. This combustion kindles the potassium, which instantly burns with a kind of explosion. One grain of potassium, when thrown into water, evolves 1.0625 cubic inches of hydrogen gas. Potassium, in like manner, decomposes the

water, with which alcohol, ether, and other similar fluids are always contaminated. The liquid, in which it can be preserved for the greatest length of time unaltered, is newlydistilled naphtha: Oil of turpentine likewise answers pretty well. Hydrogen gas dissolves it in considerable quantity when assisted by heat, and forms a compound gas, to which Davy has given the name of pot-assureted hydrogen,

It combines with various doses of oxygen, and of course forms different oxides. The peroxide is readily formed by fusing together potassium and potash. It has a brown colour when hot, but on cooling becomes grey. When exposed to the air, it absorbs more oxygen, and becomes potash. There is reason to conclude from some of Mr Davy's recent experiments, that potassium is capable of uniting with a greater proportion of oxygen than exists in potash, and of forming a peroxide, which readily gives out oxygen when heated.

Potassium combines readily with sulphur and phosphorus, and with all the metals hitherto tried. These alloys are destroyed by water or air, the potassium being converted into potash, and the other metal set at liberty. One part of potassium renders 70 parts of mercury solid, and forms with it a soft amalgam, which is speedily decomposed by water, hydrogen gas being evolved, potash formed, and the mercury set free. Potassium is capable of decomposing all the metallic oxides, and likewise all salts hitherto tried. A very copious set of experiments on the subject was made by Thenard and Guy Lussac. Most of the decompositions were accompanied by combustion.

It follows, from Mr Davy's ex

of 86 potassium,

14 oxygen,

100

or the oxygen in potash amounts to about one seventh of its weight. 4. The properties of sodium are very analogous to those of potas

sium.

It is a white metal like silver, and at the common temperature of the atmosphere is solid, but very malleable, and so soft that two pieces of it may be welded together by simple It begins to melt at 120°, and is completely fluid at 180°. It does not volatilize at a heat sufficiently strong to melt plate-glass. Its specific gravity is 0.9348.

pressure.

Its affinity for oxygen is similar to that of potassium. Like potassium, it is converted into soda by simple exposure to the air, and when thrown upon water, decomposes that liquid rapidly, hydrogen gas being evolved. It is not soluble in hydrogen gas. Hence the reason why it does not burn when thrown upon water like potassium. Like potassium, it combines with various doses of oxygen. It combines likewise with phosphorus, sulphur, and the metals, and forms alloys as easily decomposable as the alloys of potassium.

Soda, according to the experiments of Mr Davy, is composed of 78 sodium,

22 oxygen,

100

Thus it has been ascertained, that both the fixed alkalies are metallic oxides a discovery quite unexpected by chemists, which destroys the propriety of the term oxygen, invented by Lavoisier; since that principle is not only the former of acids but of

rather unforeseen shock to the theory of that ingenious philosopher, and points out the impropriety of con structing a language upon the prin ciples of theory alone, as was the case with the chemical nomenclature contrived by the French chemists, a nomenclature extravagantly praised, but defective and erroneous in some of its most material parts.

5. The striking analogy between the four alkaline earths, barytes, strontian, lime, and magnesia, and the fixed alkalies, rendered it probable that they were similar also in their composition. Indeed it had been long the opinion of certain chemists, that the earths are metallic oxides, and Lavoisier had stated the probabi lity of this opinion in his Elements. It was natural for Mr Davy, after having succeeded in decomposing the fixed alkalies, to apply the same me thod of analysis to the alkaline earths; but his first attempts were not crown. ed with success.

He tried to decompose them by the action of the galvanic battery under naphtha, having previously moistened them slightly to make them conductors. In these cases inflammable gas was evolved, and the earths, where in contact with the ne gative wires, soon became dark-coloured, and small metallic points appeared, which became white when exposed to the air. In these experi ments there was reason for believing that the earths had been decomposed; but the quantity of metallic mat ter evolved was so minute as to elude examination.

An attempt was made to decompose the alkaline earths, by heating them with potassium in glass tubes; but it did not succeed. The earths, indeed, became dark-coloured, but