on a new power of the electric current of a nature, bearing some analogy to the magnetic action, or possibly resulting from it; but this in the present state of our investigation would be too bold an hypothesis, especially as it is also a very vague one. 50. But whatever conclusions we may form, the phænomena are certainly interesting, and promise to afford abundant matter for future research. Meanwhile, it is not improbable that many phænomena of minute intestine motions usually attributed to capillary attraction, generation of heat, or other causes, may be referrible to similar causes. One I cannot forbear to mention, from the striking external resemblance of the effect to some of those described in this Paper. I mean the motions described by M. Amici in the sap of the chara, as originating in certain rows of globules disposed in the direction of the stream. The motion of the fluid in the vicinity of these globules has been attributed by M. Amici himself to electricity developed in some unknown manner by them, and is so similar to what takes place when a stream of electricity is made to pass over a row of minute globules of mercury under a conducting medium, that one has difficulty not to presume an analogy in the causes. Slough, Jan. 6, 1824. J. F. W. HERSCHEL. NOTE. 51. Since writing the above, Mr. Faraday has been so good as to show me a Paper, published by M. Serrulas, in the Journal de Physique for 1821 (vol. 93), in which are related one or two of the appearances described in this Lecture, and other very curious ones referrible to the same causes (though not apparently regarded by him as being so). As the phænomena themselves are interesting, and the theory of them adopted by him is (as I shall easily show) insufficient, I shall be pardoned for extracting the whole passage from his Memoir; regretting at the same time not having been able to find a former Paper on the subject, mentioned by him, in which his explanation is given at full length. 52. The phænomena in question relate to the singular gyratory motions assumed by alloys of potassium when floated in small fragments on mercury under water. After noticing those of the alloy of bismuth, which he describes as particularly forcible and lasting, he goes on to say, 53. Ne seroit-il pas intéressant d'étudier l'action électrique qui se manifeste dans cette circonstance pendant l'oxidation du potassium."-" Elle me semble digne d'attention pour sa liaison avec la décomposition de l'eau dont elle depend unique ment. * * 54. "La pellicule légère qui se forme dans ce cas n'est que le bismuth divisé provenant de l'alliage retenant entre ses mole cules des bulles d'hydrogène extrêmement fines. Cette pellicule, comme je l'ai dit, est attirée avec une grand promptitude par les substances métalliques mises en contact avec le mercure sur léquel les fragmens d'alliage sont en mouvement. 55." J'ai du considérer cette pellicule comme jouissant de l'électricité positive, attendu qu'elle se porte vivement vers l'extrémité negative d'une cuve en activité, et qu'elle est au contraire puissamment repoussée par le pole positif. Si les deux conducteurs touchent seulement l'eau du bain, l'attraction et la repulsion ont lieu dans le sens indiqué. L'effet est encore le même si l'un des fils touche le mercure, et l'autre l'eau. La pellicule se fixe au pole negatif d'où elle est chassé avec force par l'approche du pole opposé. Elle s'écarte, et l'hydrogène de l'eau décomposée se dégage sur ses bords qui dans ce cas font partie du conducteur et le terminent. Si les deux fils plongent dans le mercure il est bien entendu qu'il ne se manifeste plus rien. 56. "Quand, au lieu d'eau simple, le bain de mercure est couvert d'une dissolution peu chargée du chlorure de sodium, le tournoiement des fragmens est plus lent. L'hydrogène produit se trouve engagé et retenu presqu'entièrement par la pellicule du bismuth; l'eau en devient nebuleuse. A l'instant où l'on a plongé dans le bain une tige métallique, on remarque autour de celle-ci un frémissement; les mouvemens cessent et sont arrêtés tant que la tige rest plongée; elle fixe la pellicule dans toute l'étendue du bain; les fragmens d'alliage y sont emprisonnés; mais aussitot que la tige est retirée, l'effluve d'hydrogène écarte la pellicule, et les mouvemens recommencent. 57. Un fil plongé sur un point quelconque d'un bain ou tournoie l'alliage, même dans un endroit éloigné de ce tournoiement, la partie plongée de ce fil se couvre en peu de temps d'une multitude des bulles d'hydrogène. Ne pourroit-on pas encore d'après cette observation, qui prouve que toute la surface du bain est parcourue d'hydrogène, ne pourroit-on pas trouver dans l'émission rapide et abondante de ce gas la cause de l'électricité, quand on considère que l'air atmosphérique dirigé avec une soufflet sur un carreau de verre donne à ce carreau l'électricité vitrée; ou bien cette effluve d'hydrogène qui pousse vivement sur le mercure les molecules de bismuth non amalgamé, qui les réunit sous forme de pellicule, produit entre les deux métaux un frottement qui développe cette électricité." 58. From these passages it seems natural to collect, that M. Serrulas conceives, 1st, the production, motion, &c. of the pellicle on the surface to originate in the actual mechanical impulse of streams of hydrogenous matter (effluve d'hydrogene), radiated in all directions from the potassium in the moment of its oxidation. That, 2ndly, this bodily radiation of hydrogen is propagated along the surface to any distance. That, 3rdly, the hydrogen disengaged in bubbles from a metallic wire plunged into the mercury is this actual radiant hydrogen, conveyed and collected on its surface from all parts of the mercury. That, 4thly, the friction of the hydrogen so radiated produces the electricity, and not the electricity the hydrogen. And, lastly, that the gyration of the fragments themselves is a consequence of the re-action of the hydrogen they dart out during their oxidation by the water. 59. All these phænomena, however, are much better accounted for on the principles of this Lecture, from a knowledge of the properties conferred on mercury by alloying it with potassium; but, first, it is necessary to premise, that the mere contact of a metal capable of amalgamating, even for an instant, communicates its peculiar properties, almost in the moment of contact, to the whole mass. The experiments in Art. 33, abundantly prove this; and it may be readily shown also by the following. Let a quantity of mercury be placed in a vessel of muriatic acid; no action takes place; but if touched with a zinc wire it presently becomes covered with bubbles, copiously disengaged from every part of the surface. 60. In the circumstances of M. Serrulas's experiments, it is therefore obvious that his mercury must have been always sensibly impregnated with potassium and the supernatant liquid, a solution of potash; and that it was so, is proved by the effects of the electric current, which agree precisely with those I have stated, as being always produced in such circumstances (Articles 18, 28); but the cause assigned to these effects by Mr. S. viz. the electro-positive energy of the pellicle, is proved not to be the real one by the simple fact, that the violence of the motion is always proportional to the cleanliness of the surface, and is greatest when there is no pellicle at all; besides which the pellicle here consisted of metallic bismuth, a substance incapable of producing any such effect as shown in Art. 38. 61. The gyration of the fragments is produced as follows: a strong Voltaic excitement takes place at the point of contact of two metals so different as mercury and potassium. The mercury becomes strongly positive, and the floating fragments negative. The circuit is completed by the alkaline liquid; and the mercury, being alloyed with a portion of potassium, and being itself the positive pole of the combination, we have here the case of Art. 21; and the result, as stated by M. Serrulas, is precisely as in that experiment, the currents radiating from the point of immersion. These once produced, drive before them the fragment in which they originate, in the direction in which it exposes the greatest surface to their action. 62. The attraction of the pellicle to a metallic rod plunged into the mercury is also a direct consequence of the alloy of potassium present in the mercury, as is also the disengagement of gas from the wire. It is, in fact, precisely the experiment described in Art. 25, and has nothing whatever to do either with the floating fragments, or with any hydrogen they may be discharging at the time, farther than that their contact serves to furnish potassium to the mercury. 63. It is needless, therefore, to push this examination further, as all the phænomena observed by Mr. S. are only particular cases of those I have described. With regard to the radiant hydrogen producing currents by its impulse, I would ask how it happens that currents are produced (when the positive pole is placed in contact), while a thick and tough coat of oxide covers the whole surface; and, one would think, must effectually defend it from the action of the hydrogen. Yet we have seen, in Art. 18, that the currents continue their course under this crust; and it will hardly be contended, that the hydrogen finds a passage between the oxide and the metal. London, Jan. 13, 1824. J. F. W. H. ARTICLE XII. Nitric Ether. By Mr. Whipple. (To the Editors of the Annals of Philosophy.) GENTLEMEN, Elaboratory, London, Sept. 17, 1824. SINCE to give my opinion on the directions given by Dr. Ure in his Chemical Dictionary, for conducting a retort distillation of nitric ether, would be γλαυκα εις Αθήνας κομιζειν, 1 shall feel obliged if favoured with an insertion of the following question: Whether the directions for the management of a glass retort in forming nitric ether, be correctly stated in Dr. Üre's Chemical Dictionary? I remain, Gentlemen, your most obedient servant, ARTICLE XIII. Astronomical Observations, 1824. Bushey Heath, near Stanmore. Latitude 51° 37' 44.3" North. Longitude West in time 1' 20.93′′. Occultations of stars by the moon. Sept. 4. Immersion of a small star. 19h 10 540 Siderial Time. 3 28 46-25 ARTICLE XIV. Remarks on Solar Light and Heat. By B. Powell, MA. FRS. (46.) I concluded a former portion of these inquiries with some remarks on the small development of a heating effect which is observable exterior to the cone of light formed by a lens. The investigation of its nature appearing to me a topic of considerable interest as bearing upon many other parts of the science of light and heat, I have been led to try several experiments upon the subject. The results of these trials in which the circumstances and conditions of the case have been varied in several different ways, I here propose to give in a tabular form, and to introduce them by a few remarks on the nature and object of the experiments, as well as on the sort of conclusion, which can safely be deduced from them. (47.) The existence of the effect in question being admitted, two suppositions obviously present themselves as to its nature. It may be attributed to certain rays of light refracted to a position beyond the principal body of rays which go to form the focus. These may be rendered invisible or nearly so from the proximity of other rays of infinitely superior intensity. And thus the phenomenon may be nothing more than simply the ordinary heating effect of these rays displayed on the black bulb of the instrument. Again, it may be supposed (which seems to have been the idea of the first observer of this and kindred phenomena), that it is owing to some sort of radiant heat. From his analogical view of the subject, it would have followed that these were rays of a peculiar kind different from those of terrestrial heat, and exhibited as existing in a separate state from the rest of the solar rays by the refractive powers of the lens; rays in fact of a sort of intermediate character between light and common heat. If, however, because we cannot see the rays producing this effect we should think it necessary to infer that they must be rays of simple heat, or if we had any better experimental reasons for such a conclusion, still it would not, I conceive, be at all necessary to suppose any thing peculiar in their nature, or that they were really an emanation entirely sui generis; for there would still be no proof whatever that they had passed through the thick glass of the lens in the form of rays of simple heat. It is obvious that we may, in all respects, as well suppose them to have originated, or have been separated in some way from the deflected rays of light after their passage through the lens; and it would seem that such a supposition is the more incumbent on us, when we admit what has, I conceive, |