any the nowsupo The mare ased ir 15 72 cooling, will partly sink E IF G H B press upon the mer- As d C D to compressing power by the compression of the air. All changes of temperature are easily perceived on the narrow neck of the flask much more accurately than on any thermometer; for an increase of temperature amounting to one degree (centigrade) makes the water rise 27 lines, its temperature supposed to be about 15°. If the temperature is considerably higher or lower, the changes of course will be either greater or smaller. The scale being divided into one-fourth part of a line, and one-eighth being easily perceived by the eye, it is evident that too° cannot escape observation, and thatozóis by no means difficult to observe. It is scarcely necessary to add, that the temperature of the liquid is to be ascertained by a thermometer, at the beginning of the experiment. If the experiment be made quickly, and no per mea mea 1 sons present beside the observer, the difference in the height of the mercury before and after the experiment will generally) one-eighth of a line; frequently, however, one-fourth. In the first case, it announces a change of temperature amounting to not quite zob, too in the second to hardly tódo. If the experiment be performed slowly, the difference may be one-half, and even one line. In every case the mean height between these two observations is to be taken. By a long series of experiments, of which the most accurate were made at a temperature of 15-16*, a pressure equal to one atmosphere has produced a compression = 0.000047 of the original bulk of the compressed water. Several alterations on the pressure, from one-third to five atmospheres, were tried, and agreed in proving, that the compression is in direct proportion to the compressing power. The same result had been deduced by the author from his former experiments, which, however, were influenced by the giving way of the metallic vessel ; the expansion of which must likewise be in proportion to the pressing power. It seems pretty evident that no heat is produced by this condensation of the water, the limit between mercury and water being, after the experiment, on the same place as before; the insignificant elevation of temperature must be considered as a necessary result of the contact of the observer during the experiment. Even after a pressure of five atmospheres, the difference of temperature was not quite tób, and in general neither greater nor less than that, if only a pressure of one atmosphere had been used. It was, however, possible, that the expansion of the water when the pressure had ceased, would absorb the heat produced before by the compression; therefore a thermometer of Breguet, on which a difference of Loth of a , degree may easily be perceived, was placed in the water in the large cylinder, and exposed to the greatest compression which could be procured, but not the least trace of any change in the temperature was observable. The manner in which these experiments of Prof. Oersted agree with those of Canton is really interesting. The English philosopher had at 64° Fahr. = 151 centigrade, a compression of Tootoo by pressure equal to one a ' atmosphere, and at 34° Fahr. = 110° centigrade, it was too 07: This rather unexpected result may easily be explained by small differences in the temperature, but it does not, on either side, deviate much from the result Prof. Oersted obtained, which was TO 00007 4 49 100000 4.7 the g to pe and ese Ots, 6, msed to the er. his he List Astronomical Observations, 1822. By Col. Beaufoy, FRS. Bushey Heath, near Stanmore. Nov. 21. Immersion of Jupiter's first s 16h 14' 49" Mean Time at Bushey, satellite.. ? 16 1610 Mean Time' at Greenwich. Nov, 23. Immersion of Jupiter's first < 10 43 19 Mean Time at Bushey. satellite. ? 10 44 40 Mean Time at Greenwich, Nov. 25. Emersion of Jupiter's first s 7 21 20 Mean Time at Bushey. satellite.. 27 22 41' Mean Time at Greenwich. Nov. 27. Emersion of Jupiter's second 950 15 Mean Time at Bushey, satellite. 9 51 36 Mean Time at Greenwich. Nov. 29. Immersion of Jupiter's third satellite. * Dec. 7. Emersion of Jupiter's first 16 41 20 Mean Time at Bushey. satellite 16 42 41 Mean Time at Greenwich. Dec. 11. Emersion of Jupiter's second § 15 04 0.0 Mean Time at Bushey, satellite 15 05 21 Mean Time at Greenwich. { ARTICLE IX. Analysis of Uranite from Cornwall. By. Richard Phillips, FRS. L. & E. &c. This mineral has been found in several of the Cornish mines; the crystals are sometimes of a yellow colour, more especially those which occur in Tin Croft copper mine, near Redruth; while in Gunnis Lake copper mine, at the eastern extremity of the county, it is met with of a beautiful deep-green colour. The primary crystal of this substance is a right square prism, and there is no difference in this respect between the yellow and green crystals; the modifications of this form, with their varieties, have been described by my brother (Mr. W. Phillips), in the third volume of the Geological Transactions. Both varieties of uranite have been subjected to chemical examination by the late Rev. Mr. Gregor. With respect to the yellow crystals, he states (Phil. Trans. 1805), that beside oxide of uranium, they contain some lime, silica, and oxide of lead; and, he observes, that “the green crystals differ in no respect * According to the Nautical Almanac, the immersion of this satellite should have taken place at 1726' 56"; but although I placed the telescope at 176 09' 29", the *Eclipse had previously occurred. As from the yellow, except in containing a little of the oxide of Oxide of uranium, with a trace of oxide of lead., 74.4 8.2 15.4 Loss. 2.0 100.0 M. Berzelius, in his Nouveau Système Mineralogique, has given an analysis of the uranite of Autun: he says, “I have found that this mineral is a compound of oxide of uranium, with lime and water; in fact, that it is a true salt with a base of lime in which ; the oxide acts as an acid.” He further states, that the oxygen of the uranium is three times, and that of the water six times, the oxygen of the lime; there is, however, he observes, a slight excess of oxide of uranium and of water. The results of this analysis are thus stated : Lime .... 6.87 Oxide of uranium 7215 Water. 15.70 Oxide of tin .... 0.75 Silica, magnesia, oxide of manganese. 0.80 Matrix 2-50 nded to di uranit 98.77 “ The same mineral," continues Berzelius, “is met with in Cornwall , but it is of a very fine deep-green colour; this colour is owing to the presence of a certain quantity of arseniate of copper, which is an accidental admixture. When this uranite is treated with soda by the blowpipe, it gives white metallic globules, composed of arseniuret of copper." With the intention of procuring some peroxide of uranium, I dissolved a quantity of the green uránite in nitric acid ; the oxide of uranium was precipitated by ammonia, and the oxide of copper dissolved by excess of it. In order to free the oxide of uranium from any arsenic acid which it might contain, I boiled the precipitate in a solution of potash; on adding a portion of the filtered solution to nitrate of silver, an abundant yellow precipitate was formed, which had the appearance of arsenite of silver; but as arsenious acid does not, I believe, exist in nature combined with any metallic oxide, and as also the mineral in a Perime miedo = 17 way sin sping to the hat und ach gen RES, ght question had been dissolved in nitric acid, it was evident that the yellow precipitate could not be arsenite of silver. As phosphoric acid is well known to afford ayellow precipitate with oxide of silver, I suspected the presence of this acid, and I found that the alkaline solution gave a blue precipitate with sulphate of copper; and when it was saturated with an acid, mixed with ammonia and muriate of magnesia, the well-known minute crystals of phosphate of ammonia and magnesia were formed. Under these circumstances, it appeared to me worth while to subject the uranite to another analysis, and I proceeded as follows: One hundred grains of the green uranite of Cornwall were dissolved in dilute nitric acid; half a grain of silica remained undissolved. In attempting to saturate the solution previously to adding nitrate of lead for the separation of the phosphoric acid, I found that precipitation occurred long before sufficient potash had been added. As this free nitric acid would dissolve the phosphate of lead formed, I decomposed the nitric solution by boiling it with excess of potash, and then having added excess of acetic acid to the alkaline solution, nitrate of lead gave an abundant precipitate of phosphate. I prefer acetic acid for this purpose to nitric, because as acetic acid has scarcely any action upon phosphate of lead, it is not requisite to take the trouble of avoiding slight supersaturation. The phosphate of lead thus obtained, after washing and drying, weighed 80 grains, equivalent, according to Dr. Thomson, to 16 grains of phosphoric acid ; the oxides of uranium and copper were redissolved in nitric acid, and the solution being added to ammonia, the oxide of copper was dissolved, and that of uranium precipitated; the latter, after washing and drying, weighed 60 grains, and the oxide of copper, after ebullition with , potash, weighed 9 grains. The ammoniacal solution contained 9 no lime. It appears, therefore, that 100 grains of this substance contain Silica... 0:5 Phosphoric acid. 16.0 Oxide of uranium 60.0 9.0 Water 14:5 IN jur of ite lic Oxide of copper 100.0 I attempted to determine the quantity of water by direct experiment; for this purpose 50 grains of the mineral were heated on a platina crucible by a spirit lamp, 8.5 grains were lost = 17 per cent. This experiment was repeated with a precisely similar result, and no further loss was occasioned by exposing the mineral to a strong red heat. If, however, we add 17 to the acid and oxides, there will be an excess of 2-5 over |