electrolytic compound present in the air, as well as we suppose one to be contained in water, and that the electro-negative constituent, or the anion of that electrolyte, is our ozone. The passage of electricity from the points of charged bodies into the surrounding air being in fact nothing but the act of the restoration of a broken electrical equilibrium, or a current, it is not difficult to conceive how ozone is set free near the points of emission. Our supposed electrolyte being present in the atmosphere, requires only to be placed within the circuit of such a current in order to be electrolysed, or to have its anion, ozone, separated from its cation. If all these suppositions be correct, it follows that the electrolysis of our ozonic compound will be most vigorous where the emission of electricity is most abundant, and that consequently, at such a spot, the strongest smell of ozone will be perceived, and platina or gold acquire the highest degree of negative polarity. Now experiments prove that such is really the case. That the peculiar odour perceived when any terrestrial object is struck by lightning has something to do with ozone, cannot be doubted. We have been hitherto profoundly ignorant of the nature of that odour, and everything said and conjectured about it by ancient and modern philosophers must, in my humble opinion, be considered as totally unfounded. We know the fact only, and nothing more. The smell produced by lightning is usually described as being either sulphureous or phosphorous. Twice in my life I had an opportunity to observe this odour, once in the church of my native place (Mezingen in Wurtemberg), many years ago, another time in my own house at Basle, only last summer. The second case being still fresh in my memory, I shall say a few words about it. The object struck by lightning was a small chapel situated on the middle of the bridge of the Rhine, and about 200 yards distant from my lodgings. Immediately after the stroke had taken place, not only my house, but also the houses of my neighbours, were filled with a bluish vapour, and a pungent smell was perceived. Six hours after the occurrence I entered into a parlour which had not been opened all the day, and I could still perceive the peculiar odour. My testimony is certainly not wanted to establish the fact, that lightning always causes the disengagement of an odoriferous principle; but I think that, on account of the great mystery which is still hanging over that phænomenon, the number of observations and statements about it cannot be too much increased. The fact related offers, besides that peculiar interest, that the smell was perceived at a comparatively great distance from the object struck by lightning. As far as my observations go, they incline me to consider the odoriferous gaseous substance set at liberty by the agency of lightning as ozone. Lightning being the same phænomenon on a large scale as the electrical spark or brush is on a small one, and our supposed electrolytic compound penetrating the whole atmosphere, electrolysis must take place, and consequently ozone be disengaged to a considerable amount, as often as lightning crosses our atmospheric air. The assertion of some observers, that the odour is of a sulphureous kind, and the statement of others, comparing it with the smell of phosphorus, may easily be reconciled to each other; for I have remarked that ozone, when somewhat condensed, is rather pungent, whilst the same substance mixed up with a large quantity of air, possesses a phosphorus smell. It is well known that the generality of people call any pungent odour sulphureous. Hence, if it happens that the odoriferous principle set free by lightning reaches the observer in a condensed state, he will describe it as sulphureous, but like phosphorus when inhaled mixed up with a good deal of air. Hence it follows, that the nearer the observer happens to be placed to the spot where a stroke of lightning takes place, the more pungent will be the smell perceived by him. The property of platina to assume negative polarity in a medium containing free ozone, seems to offer an excellent means to ascertain the presence of that principle in the atmosphere. It appears, therefore, to be desirable to make experiments on that subject, and to place, for that purpose, platina stripes (not being insulated) in elevated regions, particularly on days when thunder-storms are taking place. Before closing this paper, I must not omit to put a question of some importance. Does the electrolytic compound mentioned exist in our atmosphere quite independent of its aqueous vapour, or is it (the electrolyte) carried into the air by the evaporation of water? It is a matter of course, that this question can only be answered by experiments, and I have not yet found time enough to make them. Supposing the electrolyte to be carried into the atmosphere by the evaporation of water, the electrical brush should not produce any smell when passing into absolutely dry air, and the quantity of ozone disengaged would, cæteris paribus, be proportional to the quantity of aqueous vapour present in the atmosphere; i. e. would depend upon the hygrometric state of the latter. It is hardly necessary to say, that problems of the highest scientific importance would be raised, in case it should turn out that ozone can be produced in dry air. Be that, however, as it may, the ubiquity of our elec trolyte can hardly fail acting a most important part in the household of nature; and it is not impossible that the electrical phænomena taking place within our atmosphere, the real cause of which is still covered in darkness, are closely connected with the workings of our presumed compound. The fact of philosophers having not yet had the slightest notion of the existence of such a body is, I presume, no argument against its existence. If we suppose the electrolyte in question to be a substance closely resembling water in its chemical and physical properties, and existing in the latter fluid as well as in the atmosphere, only in very small quantities, it is easily conceivable why its existence has not hitherto been observed. I readily allow, however, that many researches, many experiments, must still be made before we arrive at certain results, at complete certainty, regarding the subject of ozone. Convinced as I am of its great scientific importance, I shall not fail devoting all my leisure time to its close investigation, and to sifting a matter to the bottom which promises to yield so rich a harvest of results. I should feel indeed very proud, if the British Association would honour me with the charge to present them an account of my researches next year. It would be not right if I did not expressly state, before finishing my paper, that I owe most of the results above mentioned to a pile constructed upon my friend Mr. Grove's principle, an arrangement which cannot be too highly thought of. Bâle, August 2, 1840. C. F. SCHÖNBEIN. Second Report upon the Action of Air and Water, whether fresh or salt, clear or foul, and at various temperatures, upon Cast Iron, Wrought Iron, and Steel. By ROBERT MALLET, M.R.I.A., Ass. Ins. C. E. 140. SINCE my former report upon this subject was submitted to the British Association, as now printed in its Transactions, additional interest and importance has been given to every branch of the inquiry, as to the durability of iron under its various circumstances and conditions, by the rapidly-increasing introduction of iron vessels to navigation in the most difficult and lengthened voyages. Amongst the several problems of a strictly scientific character requiring solution before the use of iron ships for distant voyages, or their economic adoption, under any circumstances, can be pronounced certain, is the great question of their durability as compared with those of timber; and it is hoped that the experiments made or in progress under the auspices of this Association, and about to be detailed, will render, in part at least, a satisfactory reply thereto. But, besides the desirableness of prolonging the existence of iron ships, it is of the utmost importance to prevent the formation of rust at all upon them under water, which, once produced, affords a "nidus" for the growth of marine animals and plants by which the ship's bottom is rendered foul, and her sailing qualities are greatly interfered with. These causes of foulness are found to adhere with the utmost obstinacy to the oxidized iron. It is part of our object to endeavour to find remedies for these evils. 141. The present report contains the first set of tabulated results which I have obtained as to the amount and nature of corrosion of cast and wrought iron under several different conditions of exposure to the chemical action of air and water, whether of the ocean or of rivers, &c. And as this subject essentially consists of two distinct parts, or is to be viewed in two different lights, namely, as a chemical or purely scientific inquiry, and as a technical one, from which useful practical results are to be derived, and as some portions of it, viewed in the former light, are still under experiment, and likely to be so for some time to come, I purpose, on this occasion, to reserve the purely scientific consideration of the subject, as far as pos sible, for a future and final report, and confine the present to the results and their modifying conditions which have already been obtained, and are of practical value and importance to the civil engineer, the iron founder, or the iron-ship builder. 142. I proceed, then, to state the general nature of the accompanying tabulated results of experiment. The first five tables contain the data and results of the chemical or corroding action of sea and fresh water on cast and wrought iron under five several conditions of experiment, continued during a period of between a year and thirteen months. It will be seen that these five first tables, so co-ordinate with each other as to form one connected and comparable whole, by which have been determined the relative rates of corrosion, and the absolute amount thereof, for eighty-five several sorts of cast and wrought iron, under each of the following conditions, viz. 1. In clear sea water, at temp. IV. In foul river water, V. In clear river water, دو دو دو وو 46° to 58° Fahr. 46° 58° 115° وو دو 36° 61° دو 32° 68° 143. During the period in which the several sets of specimens have been immersed, the five waters acting on them have been examined as to their physical and chemical properties. 144. The water of No. 1, that of Kingstown Harbour, contains, in a cubic foot, 12661 grains of solid matter, which analysed with precaution in the usual manner, had the following constitution reduced to per cent. : It I could not detect any chloride of potassium or carbonate iron, said to be occasionally present in minute quantity in sea water. The amount of organic matter is very variable. therefore appears not to differ much in composition from the waters of the British Channel, but considerably from those of the Mediterranean and the Atlantic Ocean, as given in the best |