donia rangiferina. Along with the Lichens, the various dyes which they furnished by the action of different reagents were exhibited. Prof. Balfour also exhibited specimens of Polypodium alpestre, which he stated was common in the Scotch highlands, although only recently pointed out as a British plant by H. C. Watson, Esq. On the Effect of Sulphate of Lime upon Vegetable Substances. About six weeks since I was engaged in making various experiments on the effect of sulphate of lime upon vegetable substances. A portion of the substances then used by me was thrown carelessly aside, and upon returning to my experiments about a fortnight afterwards, I was surprised to find that decomposition had not taken place in those parts of the vegetables which had been subjected to the action of the sulphate, while those which had not been so treated were completely decayed. Among the articles experimented upon were a number of potatoes, each of which was affected by the prevalent disease; some of these remain sound to the present day, the others have some time since completely rotted away. Subsequently, I procured some more potatoes, and also some beet-roots, the former being, as far as I could judge, all diseased. I divided the potatoes into three portions. One lot I placed in a vessel with a weak solution of sulphuric acid, and from thence I placed them in a solution of weak lime-water. In the second lot the process was reversed, that is to say, the potatoes were first placed in the lime-water, and then in the acid. The third lot was left untouched. Ten days afterwards I examined the potatoes, and found, as I expected, that the potatoes which had not been treated with the sulphate were rapidly decaying; those which had been first placed in the solution of lime and then in the acid were more nearly decomposed; while those which had been treated in the mode first described remained as sound as when first taken in hand. Upon being cut open the diseased part of the potatoes was not found to have spread internally, and the flavour of the root was in no degree affected by the application of the process, nor do I think that its germinating power was injured by the effect of the sulphate. The effect upon the beet-roots was similar to that produced upon the potatoes, and which would seem to be somewhat analogous to that of galvanizing metals, viz. protecting the substances from the effect of atmospheric agencies. I may add, that muriatic and other acids have been employed by me on other occasions with equal success, the only agents required appearing to be those which will most readily produce a sulphate in contact with the substances required to be preserved. As at present it does not appear that any means can be successfully adopted to prevent the potato from becoming diseased while in the ground and arriving at maturity, it would certainly be of immense advantage if anything could be discovered by the use of which the roots when taken up could be prevented from that absolute decay and irreparable loss to which potatoes affected by the disease are liable. The results which I have described seem to me to point to the possibility of arresting this loss. How far the plan suggested may be practicable or applicable upon a large scale, my present very pressing and numerous engagements have hitherto prevented me from ascertaining. I do not think that any insuperable difficulty exists with respect to the application of the proThe acid employed by me was very weak, about 1 part to 200 of water; the lime-water was about the consistency of milk. The materials are not therefore expensive; and when the value of the crop to be saved is taken into consideration, it would be a matter well worthy of being tested by some of those extensive growers of potatoes in the county in which the British Association is now holding its sittings. For my own part, I should be most happy, if by any suggestion of mine I had merely been the instrument of directing the attention of scientific men to the subject of the possibility of preserving from total destruction a vegetable so valuable and so indispensable as the potato. cess. On the Cause of the Transmission of Electricity along Conductors generally, and particularly as applied to the Electric Telegraph Wires. By the Rev. THOMAS EXLEY, A.M. From phænomena, I infer the existence of an element in great abundance, which I call electrogen; the proof will be given in a work which I hope speedily to publish, in which I have clearly proved that each tenacious atom attaches to its sphere of repulsion a number of ætherial atoms, such that the sum of their forces is exactly equal to that of the atom to which they are attached. These are uniformly disposed, and therefore, as Newton has shown, have the same effect as if placed in its centre: this may be called the attached atmosphere. Circles being described on each of these as centres, with the radius of an ætherial atom, and a sphere concentric to the tenacious atom, touch them internally, and another externally; then between the attached atmosphere and the inner sphere will be a spherical shell equal in thickness to the radius of the ætherial atom, less the diameter of the tenacious atom; the ætherial atoms in this shell are all repulsive and equal together to the attraction of the tenacious atom, and hence it may be called the neutral shell. After this succeeds another shell, whose thickness is equal to the diameter of the central atom; in this the ætherial atoms begin to attract more and more from the concave to the convex side, to the surface of which the united actions bring an atmosphere of electrogen; the electrogen is abundant, so that by the pressure of the atmosphere the centres are within the spheres of each other's repulsion. The difference of conducting power will be found in the difference of these shells. Suppose two tenacious atoms the force of one ten times greater than the force of the other, but its sphere of repulsion ten times less; calculation gives the repulsive force between the centres of its attached atmosphere, which force is one million times greater, and shows its diametrical shell contains ten times more atoms crowded in a space many times less, the difference being chiefly on the convex side. Hence electrogen cannot by any moderate force enter its diametrical shell; it will be a conductor, because the electrogen easily floats on its surface. A moderate force will bring electrogen into the shell of the other, which will prove more or less an obstruction to the passage of electrogen; it will therefore be a non-conductor and an electric. Suppose, now, the balls of a long conductor brought near the sides of a charged electric. The electrogen, tending outward from the positive side of the electric, affects the contiguous air to the conductor, and along it to the negative side, where the effect is increased by the tendency of electrogen to supply the defect on that side; when brought to the striking distance, a spark passes from the positive side and another to the negative side, and the equilibrium is quickly restored from both sides towards the middle of the conductor, although it pass but to a short distance. The passage of the spark is quite different from the conducting of the fluid; in the spark a body of electrogen forces its passage in a prepared direction, but a current is propagated along a conductor from atom to atom. Thus, in the wire of the electric telegraph, by the action of the galvanic apparatus, the lines of electrogen along the sides of the wire are affected through the whole length, and as there is a continual supply from the apparatus, the whole line is at once and continually put in motion, each atom of electrogen taking place of the next through the whole line, so that the apparatus causes the passage of the atoms nearly at the same time to proceed at the other end, distant 30, 50, 100, or 1000 miles; a greater distance requiring of course a greater intensity of galvanic action. It ought not to excite surprise that these effects are so readily produced, when we consider that the wire of itself, in certain positions, without any galvanic apparatus, would convey electricity to the earth, to which in high latitudes it always has a tendency to move along any conductors in the air; hence the air itself assists the transmission, which would be instantaneous, and of equal amount in every part of the wire, were it not for want of perfect conductibility; as soon as electrogen begins to enter at one end, an equal portion tends to go off at the other end, the current being at once produced in the atoms which occupy its whole length. On the Decomposition of Water under Pressure, by the Galvanic Battery. By JOHN P. GASSIOT, V.P.R.S. It is a well-known law, long since discovered by Dr. Faraday, that whatever may be the liquid electrolysed by the galvanic battery, and whatever may be the size of the electrodes used, the same amount of chemical decomposition takes place in each cell of the battery; if water is placed in any number of separate vessels, connected by platinum electrodes with each other, and thus introduced within the circuit of a galvanic battery, the same amount of the mixed gases will be evolved from each vessel. If, instead of allowing the gases to escape from each, such vessels are closed, a very considerable amount of pressure is obtained. The late Professor Daniel many years since experimented with a closed glass vessel, as did Dr. Leeson, but in each instance, before any great pressure was obtained, the vessels broke with very considerable violence. Will Faraday's law hold good under extreme pressure? Is there any point at which the pressure will recompose the hydrogen and oxygen evolved by the electrolysis of water? Is there any point at which water under such pressure will cease to be electrolysed? and will it, under such circumstances, continue a conductor? All these questions appear to me to be well worthy of examination; and although the experiments I have hitherto made are far from being conclusive, they prove that, as far as I have been able to obtain apparatus of sufficient strength to withstand the pressure, water does continue to be electrolysed according to the law of Faraday, and that the gases under such a condition do not recombine. My first experiments were made in glass tubes; in each end I inserted a platinum wire, and filling the tube with diluted water slightly acidulated with pure sulphuric acid, the ends of the tubes were closed by mechanical pressure. A voltameter constructed on the principle of Mr. Martyn Roberts, and a galvanometer were introduced in the circuit of a battery consisting of 10 small cells of Grove's. Many experiments were made with such and similar apparatus, but all the tubes broke long before any great amount of pressure had been obtained. Finding it was useless to expect any results from using glass, I then attempted the experiment with metal. Into a copper tube, a hole of inch diameter, and about & inch long, was bored. This was insulated by being placed on a piece of dry leather, a platinum wire attached to a platinum plate being introduced into the copper vessel, which had been previously filled with diluted water slightly acidulated. The air from the water had been carefully extracted by boiling under a good air-pump; as before, I used 10 cells of a small Grove's battery, a galvanometer and a Roberts's voltameter being introduced in the circuit, and the circuit completed by making the copper vessel negative and the platinum wire positive; when 10.5 of the mixed gases had been evolved in the voltameter, the tube burst with considerable violence; taking the capacity of the tube at ths of a cubic inch, the pressure thus obtained was about 52 atmospheres. Since that period I have had an apparatus constructed by which I can collect the amount of gas from the vessel in which it is confined, for unless some mode could be devised by which this could be effected, no satisfactory result could be expected. In all my previous experiments I calculated on being able to collect the gases by opening the vessels under water, but finding it indispensable that the apparatus should be much stronger, and consequently larger, I was compelled to use other means. The apparatus in which my experiments have since been conducted, were constructed entirely of platinum encased in solid pieces of gun-metal about 6 inches in diameter. The first had a capacity of ths of a cubic inch. In one experiment, after 103 cubic inches of the gases had been evolved, a loud explosion took place; the concussion was so great as to extinguish the two gas lamps in my laboratory; my assistant, who was observing the apparatus, saw a sudden appearance of light as of a flame round the upper part of the apparatus as the gas escaped, the leather washer driven out in perfect shreds, and from the upper valves being perfectly dry, no gas had escaped previous to the explosion. On testing the platinum vessel by nitric acid, I found it had burst, the acid acting in the copper through the platinum; this fracture must have taken place at the time of the explosion, as the wire attached to the upper part, which was the negative electrode, would otherwise have had a coating of copper, whereas it was perfectly clean. The above experiment will give a pressure of 171 atmospheres. Another apparatus was then constructed, having a capacity of ths of a cubic inch. I will not occupy the time with any detailed account of experiments which have now occupied me some years, as after an accident I have often been detained for months before I could obtain another apparatus, but I will briefly describe two which may be interesting to this Section of the Association. In the first, after 110 inches had been evolved in the voltameter, I opened the valve of the apparatus, and collected the same quantity which had been under pres sure; the capacity of this vessel beingths of a cubic inch, gives a pressure equal to 275 atmospheres. In the second experiment an explosion took place when 179 cubic inches had been evolved by the voltameter; the concussion was so loud that a friend who was in the laboratory likened it to the report of a company of soldiers firing with blank cartridge. The leather (placed between two portions of the apparatus to ensure insulation) was forced out with such strength as to pass through the hat of my assistant, who was about 4 feet from the apparatus. In this instance, presuming that the whole quantity of gases as evolved in voltameter had also been evolved in apparatus, we obtain the enormous pressure of 447 atmospheres. In one experiment we have an undoubted pressure of 275, and in the other a calculated pressure of 447 atmospheres, at which water is electrolysed and conducts without apparently offering any extra resistance to the current, for during the whole of these experiments the needle of the galvanometer remained steadily deflected. On the Corrosion of Iron-built Ships by Sugar Cargoes. The author stated that his attention had been drawn by his brother, Mr. George Gladstone, to the fact that the owners of iron-built vessels object to sugar cargoes, on account of the rusting of the metal by the saccharine juices that exude from the casks; and this had led to a chemical examination of the reaction then instituted. It was found that when pieces of iron were placed in bottles containing a solution of canesugar, the metal at the edge of the liquid soon became deeply corroded, but that which was permanently immersed in the fluid remained bright for a considerable time. The solution soon gave indications of the presence of protoxide of iron, which absorbing oxygen from the atmosphere was speedily thrown down as the red sesquioxide, leaving the sugar free to dissolve a fresh quantity of iron, the precipitated oxide in the mean time forming a deposit. After eighteen months, the liquid was of a deep red-brown colour; it became pale blue with ferrocyanide of potassium, black with sulphuret of ammonium; alkalies produced no precipitate; nitric acid peroxidized it. A portion dried and analysed gave 20-78 parts of metallic oxide to 100 of combined sugar, which is almost exactly in the proportion expressed by the formula C12 H11 011 FeO. The author, however, considered that this might differ from the true composition by an equivalent of water. No such iron compound could be formed by direct combination. In vain was it attempted to dissolve any freshlyprecipitated and well-washed oxide of iron in a solution of sugar; and almost equally unsuccessful was the attempt to do so when the oxide was liberated by means of potash in the presence of sugar itself. It was found that under all circumstances of dilution or quality of the sugar solution, iron was attacked; the presence of zinc in contact with the iron did not prevent its being acted upon; nor was there any marked difference when the salts of sea-water, or the nitrates, sulphates, or chlorides of the alkalies were added to the solution. No other ordinary metal was found to be so easily acted upon as iron. Copper was very little affected by the sugar. Lead was slowly attacked, indications of the presence of its oxide in solution being obtained after three days' exposure. Tin appeared to give the binoxide. Zinc was little affected when alone; it seemed to be dissolved more quickly when in contact with iron. It is doubtful whether mercury was touched by the sugar solution; silver certainly was not. The author regretted that his experiments did not suggest any method by which the corrosion of iron ships by sugar cargoes might be prevented. They showed rather the strong disposition to combine that there is between the two substances; and how a small quantity of sugar may eat continuously into a large sheet of iron. The attention of chemists was especially drawn to the fact that the iron enters into combination with the organic matter, not when it has already been oxidized, but only when in a metallic condition, rendering the action, as would be imagined, more complicated. On the Spontaneous Decomposition of Xyloidine. This was a description of the changes that had taken place in a specimen of xyloi dine, made by treating arrow-root with nitric acid of specific gravity 1.5. Afremaining about six years unaltered, this specimen suddenly began to give gases, and in a few weeks' time nothing remained of the original xyloidine, but in its place a light brown viscid liquid. After describing the various chemical substances of which this decomposed mass consisted, the author proceeds, "We may suppose that the decomposition of this sample of starch xyloidine has taken place in somewhat of the following manner :— some of the peroxide of nitrogen has split up into nitric oxide and nitric acid, whilst a small portion of the nitrogen has combined, as might be expected, with some of the hydrogen of the compound to form ammonia, and a larger quantity has combined with carbon and hydrogen to form prussic acid. During this process oxygen must have escaped as such, or combining with carbon have passed off as carbonic acid, or it may have been consumed in the formation of the slightly acid principle which has been described as found in considerable quantity among the resulting solids. "Whether the ammonia and the nitrous fumes have reacted upon one another with the formation of nitrogen gas and water, I know not. "The separation of so much carbon in the form of cyanogen must be looked upon as the principal cause of so much water being produced, for the viscid mass is essentially a strong aqueous solution of the organized bodies. A very large portion of the starch, freed from its combined nitric acid, has remained in a gummy condition, perhaps as dextrine, though it was certainly not of the variety colourable by iodine; whilst the change had advanced further with another portion, and it was converted into sugar. These substances, with traces of a bitter principle, and of a singular odoriferous substance, were the only products of decomposition, at least as far as I could detect." On the Conduction of Electricity by Flame and Gases. th A somewhat extended series of researches has been recently carried out by M. Edmond Becquerel with a view to determine the conducting power of flame and of hot air. These investigations have led M. E. Becquerel to conceive that he has proved the conducting power of both for electricity. The apparatus employed was a platinum tube, with the conducting wire passing through it. Mr. Grove has adopted a somewhat different arrangement. This consisted of a glass tube, with two copper wires inserted through corks at either end; from these within the tube proceeded a piece of platinum wire, which, by connexion with the battery, could be brought to a state of intense ignition. In this state these were adjusted at the distance of of an inch apart, and then connected with the powerful voltaic combination of Mr. Gassiot. Notwithstanding the proximity of the wires, no trace of electricity could be detected as passing through the interposed stratum of heated air. Mr. Grove inclined to the opinion, that the effect described by M. Becquerel was more analogous to the disruptive discharge than to conduction, as it was stated not to take place until the solid bodies arrived at red heat, and then to be increased by attenuating the gases, though at temperatures below that point; no degree of rarefaction allowed any electricity to be transmitted. On the Origin and Composition of the Mineral called Rottenstone. Note on the Formation of Magnesian Limestone. The author produced specimens of magnesian limestone formed by deposition from a spring near the village of Neesham upon the northern banks of the Tees. This limestone possessed the colour, general appearance and porous structure of the limestones of the county of Durham, and contained as much magnesia as some of the purer beds of magnesian limestone in that county. From the production of this limestone he reasoned as to the deposition of dolomitic limestones in general, and the relative probability of the two theories which ascribe their magnesia to the impregnation of previously existing limestones, either by sublimation from beneath, or by percolation from above. He considered both agencies inadmissible as general causes, and was favourable to the view that as a general rule magnesian limestones were de |