seen a fragment of green fluor spar and two white diamonds emit light for one hour after insolation." In preparing these phosphori, it is noticed that the peculiarity of their luminous action depends on the primitive condition of the sulphates employed. "Thus the natural crystallized sulphate of baryta affords the orange yellow Bologna phosphorus; the natural sulphate of strontium from Sicily in rod-shaped (bacillary) crystals, yields a bluish green phosphorus, and if by the action of carbon different sulphates are reduced to the condition of sulphides, their luminous action will vary." In preparing a phosphorescent sulphide with lime, or carbonate of lime, it is most convenient to add 85 parts of sulphur to 100 of the lime, or 48 to 100 of its carbonate. The materials are intimately mixed and placed in an earthen crucible in a charcoal furnace. M. Becquerel says it is necessary to pay attention to the temperature as well as to its duration. "Operating with fibrous arragonite, and heating the crucible to 500° (C.) for a time sufficient to allow the reaction between the lime and the sulphur to take place, and the excess of the latter to be eliminated, a feebly-luminous mass affording a bluish tint is obtained. If this mass is raised to a temperature of 800° or 900° (C.) and kept for five-and-twenty or thirty minutes at a point not exceeding the fusion of gold or silver, it yields a brilliant green light. The chemical composition is the same in both cases; but it is remarkable that if the process is conducted with carbonate of lime instead of with lime, the refrangibility of the light emitted does not vary with the temperature." Too high, or too prolonged a temperature destroys the phosphorescence, and charcoal furnaces answer better than coke. Among the lime preparations, those made with pure Iceland spar give, after insolation, an orange yellow light, calc spar affords a less vivid tint, Carara marble a very weak yellow light, oyster-shells yellow, chalk a scarcely visible yellow. Arragonite of Vertaison in bacillary crystals, a green of medium intensity, fibrous arragonite a dominant violet tint, with some parts green, and lime obtained from fibrous arragonite a very vivid green. If nitric acid is employed to dissolve the lime of these minerals, and it is then precipitated by carbonate of ammonia, the tints of the phosphorescence will vary according to the sources of the lime. Phosphori composed of strontium sulphides usually require less heat in their preparation than the lime series, and an excess of heat destroys their luminosity. The barium phos phori on the contrary are prepared with greater and more sustained heat. Chlorides of calcium and strontium tend to give blue and violet tints, those of barium yield green tints, while carbonates obtained from nitrates and acetates of baryta afford yellow orange phosphori, and analogous combinations of calcium and strontium give very luminous green ones. A luminous orange phosphorus from barium is made by intimately mixing powdered crystalline sulphates with 12 to 15 per cent. of lamp black, moistened with a little alcohol. When the mass is dry it is calcined in a crucible for 45 to 60 minutes, at a temperature not exceeding cherry red, or the melting point of silver. The resulting mass is powdered and calcined a second time. We have mentioned that, as a rule, these phosphori give the same tints whatever may be the colour of the light they are exposed to in order to excite them, but M. Becquerel cites three exceptional cases. 1. Sulphide of barium obtained by reducing the sulphate with lamp black, gives an orange yellow phosphorescence when illuminated by the action of the rays in the spectrum situated towards the end and beyond the violet (from lines H to P), while the effect of the rays from the blue to the violet (F to H) is to induce a redder phosphorescence. 2. The sulphide of calcium obtained from oyster-shells, which gives a red light when excited by rays from the blue (F) to the ultra-violet as far as O, has a green tint imparted to it when excited by the rays beyond O and P, which are nonluminous to human eyes. 3. A phosphorus obtained by the action of sulphide of potassium on oyster-shells, is excited to an indigo-violet luminosity by exposure to rays of that tint, while rays beyond the violet excite it to emit a blue colour. It is interesting to observe from M. Becquerel's explanations and from a beautifully-coloured plate attached to his work, that while the most luminous parts of the spectrum, the yellow, actually exert a destructive effect on the light of these phosphori, they are all capable of excitation by non-luminous rays beyond its violet extremity. We are afraid that experimenters will only succeed in making the more easy of their phosphorescent compounds, unless they possess a good deal of patience and considerable knowledge of chemical manipulation. When well prepared the varieties of colour are very distinct, and the luminous effects brilliant and pleasing. They not only afford an agreeable recreation, but they suggest curious speculations on the molecular condition of the several compounds. Light appears to excite a peculiar vibration of their particles without affecting their chemical condition; and it is most remarkable that notwithstanding the chemical decompositions and recompositions that occur during the preparation of certain sorts, their final properties depend upon the original condition in which their alkaline earths were found. THE ERUPTIONS AT SANTORIN.* We have on several occasions laid before our readers various facts concerning the interesting volcanic eruptions at Santorin, and we have now before us a valuable paper on the subject, accompanied by large and beautifully-executed maps and diagrams. The German philosophers to whom we are indebted for this work commence by pointing out certain resemblances between the Kaimeni, or "burnt," Islands of the Santorin group, and the volcanic region immediately surrounding and comprehending Vesuvius. The island of Thera, or Santorin, is approximately semicircular in form, and opposite to its western or concave side are two other islands, Therasia and Aspronisithe latter being very small-which follow the general curvature of the main island, and with it enclose a sea-basin more than five miles in diameter, in the midst of which the Kaimenis rise. Von Buch, in accordance with his well-known theory, considered the whole formation to be "a crater of elevation," formed by the upheaval of the sea-bed; but examination in this, as in most other cases, dissipates his conjectures, and shows these Santorin volcanoes to have modified the surface by the outpouring of molten matter. MM. Fritsch, Reiss, and Stübel say, "Let us imagine Mount Vesuvius and Somma to be lowered, so that the sea might enter into and partly inundate the Atrio del Cavallo, we should then obtain a distribution of sea and land analogous to that seen at Thera and the Kaimeni Islands, a smaller part of the cone of Vesuvius rising from the sea in the midst of encircling Somma." Somma is, as most of our readers will know, the name given to the ancient cone, the remains of which partially surround the newer cone known as Vesuvius, and formed in 79 during the tremendous eruption in which the elder Pliny lost his life. After indicating the analogies between Vesuvius and Santorin, our authors point out the differences, and observe that "while on Mount Vesuvius the volcanic action has always been confined to the existing "Santorin: the Kaimeni Islands." From Observations by K. V. Fritsch, W. Reiss, and A. Stübel. Translated from the German.-Trübner and Co. crater, at least so far that they have never raised by its side any other mound approaching in height and extent to the great cone, we find, in the Gulf of Santorin, each separate revival of volcanic action, characterized by its separate and special formation, which we can trace as such even under water down to a common base. These formations owe their origin to a slow emission of large masses of lava quietly overflowing at their point of issue, filling up the irregularities of the bed of the sea, and rising by degrees as islands above the water-level. The eruptions of Mount Vesuvius, on the contrary, are mostly distinguished by a totally different character, inasmuch as the melted rock, flowing from a higher or lower point of eruption down the slope of the mountain cone, spreads in long but narrow streams." An interesting peculiarity of the volcanic action at Santorin is the fight which the volcanic fires have had with the cold water of the sea. “The quantity of steam sent forth at intervals of but a few minutes was so considerable, that it often rose to a column of more than 2000 metres in height."* This magnificent display lasted for months, and acting upon the tough, viscid lava, assisted to produce the crater forms. On the 16th of May, 1866, without previous symptoms of disturbance, two small islands appeared in the Kaimeni group. "No signs of anything occurring at the bottom of the sea had preceded this event, except that new soundings showed a depth less than that which had been previously observed in the channel." The new islands, which looked like large heaps of black rock, increased from day to day, moving at the same time horizontally from north-west to south-east, as shown by accurate geometrical measurements. In April, the progress of the field of lava of Aphroessat was principally in a northerly direction, menacing thus to block up entirely the small harbour of St. George. In the beginning of May it became every day more apparent that the mass of lava had changed the direction of its onward movement, taking its course now to the south-west, in the direction of Palea Kaimeni." By the 30th of May the new islands had increased to four, and they represented the emergent portions of the lava currents, which had filled a deep sea-trough between Nea and Palea Kaimeni. The displacement of the May islands is highly curious. Our authors describe them as made up of wildly accumulated and brittle blocks, and they regard their onward movement as indicating "not only a greater extension of the igneous mass at the bottom of the sea, but also a displacement and destruc Rather more than 2187 yards, or exceeding a mile and a quarter. tion of the yielding material in a much higher degree than that occasioned by the breakers." In actions of this kind they find an explanation of the increase and decrease and total disappearance of such islands. The paper from which we have extracted the preceding information is illustrated by four large plates; the first is a reduction of the Admiralty chart of the Santorin group, with soundings of the adjacent waters; the second is a map, showing the successive enlargement of Nea Kaimeni; the third (called Plate II.) is a remarkably beautiful and interesting photograph of a model of the island and adjacent sea-bed, made by Herr Stübel; the fourth (called Plate III.) contains two fine photographs, one depicting a bird's-eye view of the island, previous to the eruption of 1866, and the other exhibiting their configuration after it, and showing the column of steam rising from the volcanic vents. These illustrations are very instructive, and will be highly esteemed by students of volcanic action. JUPITER WITHOUT SATELLITES. ON the 21st of August the remarkable spectacle of Jupiter without his attendant satellites gratified the eyes of numerous observers. In London the weather was scarcely propitious, as a number of clouds were flitting slowly across the sky, and, at convenient hours, only occasional glimpses of the planet could be obtained. In some other localities a cloudless sky offered greater facilities, but those who were only favoured with intermittent views had much reason to be gratified with the singularity and beauty of the spectacle. Of course the phrase, "Jupiter without satellites," is not literally true. The satellites had not forsaken their primary, but, by a series of remarkable coincidences, they all ceased for an hour and three-quarters to occupy visible positions at his sides; so that, in any telescope not powerful enough to show the shadows, or the bodies of those that were on his disk, his luminous globe appeared wandering alone. Jupiter is an enormous planet, the largest of our system, being 1300 times as big as our earth, and having a diameter of no less than 87,000 miles. Mr. Breen, in his "Planetary Worlds," makes the following concise remarks respecting the four satellites of this wondrous globe. He says, "The three inner satellites move all very nearly in the plane of the equator; but the fourth is slightly inclined to it. In consequence of this, and their proximity to Jupiter, the three first |