The entire revolution of the sun's perigee, in respect to the equinox, is therefore 7645793 days, nearly, or 209 Gregorian centuries and about 33 years. Since the progressive mean motion of the perigee in one year, in respect to the fixed stars, is only 11" 7693188, the sidereal revo lution of the perigee will therefore be more than five times that of the tropical. The time required by the sun in passing over mean longitude one degree of The time required by the sun's perigee, in performing the same, | Days. Hours. Minutes. Seconds. 24 20 58.1433 is above 58 years, or more exactly 21238 7 31 42.3205 The mean periodical revolution of the moon in respect to the The mean revolution of moon's perigee in respect to the equinox 3231 M The sidereal revolution of the moon's perigee The mean revolution of the moon's node in respect to the equinox The sidereal revolution of the node Time of moon's describing 1° mean motion Time required by moon's perigee in describing 1o motion 4 6.69936 3232 13 36 41.26640 6798 4 14 51.1556 by moon's anomaly - Mean motion of sun's anomaly during a synodic revolution, or one lunation, 29° 6′ 19" 2611066. - 6793 14 28 19.8703 1 49 17-17978 8 23 25 50.68531 1 50 13.0926 18 21 12 42.475 Mean LXV. Mineralogical Account of the Island of Corsica; contained in a Letter from M. RAMPASSE, formerly an Officer in the Corsican Light Infantry, to M. FAUJAS DE ST. FOND*. I SHALL now endeavour to gratify your desire, communicated to me on my leaving Paris, of having some details of my mineralogical inquiries in Corsica, and particularly upon the orbicular granite of that island, of which a single isolated block only has yet been recognised. In order to make myself master of the subject, it was me cessary to visit the interior of the Pieye d'Orezza, and I first proceeded to reconnoitre the high mountain called Santo-Pietro-de-Rostino, from which proceed the enormous masses of quartz mixed with green diallage, with which the bed of the rivulet of the village of Stazzona is encumbered. I shall not at present enter upon a detail of the reasons which should incline us to reject the improper denomination of verde antico di arezza, which was at first given to this stone. After this visit, I wished to direct my steps to Liamone by the Pieve de Caccia; but the extremely warm temperature which then reigned hindered me, and it was not until the end of August following that I undertook this journey. Before entering into the details of my excursion to Liamone, allow me to mention a new rock which I discovered in the Niolo: it is of a peculiar texture and composi From Annales du Muséum d'Histoire Naturelle, tome viii. p. 470. tion, and I never met with it before. The following is the route I took to the place where I found this beautiful rock. By moving in the direction which I traced out to myself when leaving Bastia, I not only followed some chains of mountains from N.W. to S. and from E. to W. but I also traversed several valleys, and turned considerable gulfs which separate them in various directions. When I was in the Pieve d'Ostriconi, where the chain commences which divides the island through its whole length to its southern extremity, I traversed the highest mountains which presented themselves to me, and among others that of Niolo, called in the language to the country Monte-Pertusato, because it is pierced at its summit. Its base seemed to be intersected by some detached masses, and others adhering to it, of jaspers and porphyries of great variety. I followed the valley which leads to the place called Santa-Maria-la-Stella. Between these two points, south-east from the former and south from the latter, and at an equal distance from both, there is a high niountain covered with wood, upon the western brow of which I discovered a block of stone, almost square, about four feet and a half long. It was sunk into the ground, and exhibited globular bodies on one of its sides, remarkable from their disposition and colour, and fixed in the stony mass: some were about an inch in diameter, while others were larger or smaller: all of them presented a peculiar character which I had never seen in any stone. Not more than six inches of this rock was exhibited above ground; and in order to ascertain its dimensions I took away the earth which surrounded it. I then found that it was two feet and some inches in thickness. I also observed that its angles were entire and acute ; which made me think that it had never been removed since placed there, and particularly because the part of the slope of the mountain where it was is bare; and because, among the various blocks and masses which surround it, it is the only one which is covered with vegetable earth. I could only bring away a piece weighing about 24 pounds; the rest was too large and heavy. When the specimen was detached and exposed to view, it seemed to me so beautiful and so extraordinary an appendage to to the magnificent orbicular granite of Corsica, the celebrity of which is so well known. You may perhaps think I am exaggerating, but the following is the accurate description of the stone taken upon the spot: The rock, the heart of which seems to be porphyroidal, has its paste composed of stony elements of a petro-siliceous nature, irregularly disposed in small grains, in points and in lineaments more or less rounded off, tying as it were with each other, and varying in colour in proportion to the va rious degrees of alteration the ferruginous principle, which is very abundant in this rock, has undergone: nevertheless its general aspect, when seen at a certain distance, is the reddish brown mixed with white spots shaded with red. It is in the midst of this paste that we observe regular spheroidal bodies, from one to three inches in diameter, scattered here and there at unequal distances, and imbedded in the mass: the system of the formation of these kinds of balls can only be considered as the result of a globulous crystallization, which must have taken place rapidly; and not like geodites, which would have been formed apart, and enveloped subsequently in a porphyritical substance. The method of crystallization in question is so far remarkable, that we can form no idea of it except by representing a circle into which a multitude of small stony bodies, oblong and compressed, of a petro-siliceous nature, very close to each other, must have been directed in radii, and as it were from end to end, from the circumference towards the centre of the circle, which gives them the appearance of divergent radii; and there has resulted from it a globulous solid, which with the hammer we may drive out from the place it occupies, leaving a hole of its own form behind it. The tendency of the crystallization has been such, that we see around the spherical bodies in question, in the paste of the stone, and round the spheres, the matter of the paste itself, which, according to the tendency it had to approach it, has formed a kind of aureolus, or zones, which surround several of the bowls, which may be more casily remarked than deVol, 30. No. 120. May 1808. scribed: |