Hence the mineral is apparently a mixture of mercuric sulphide, antimonic acid (Fremy's-Sb2O,. 5H2O,* or H,Sь2O,. 3H2O), and an antimonate of calcium, mercury, and triad antimony (R'O)4 of the formula Sb2O3 .(Sb2O5)s, corresponding to a normal antimonate-M2O. Sb2O, or M'SbO3. = 25 It differs noticeably from all the natural antimonates hitherto described, in that these are strongly basic, while the mineral now described contains a surplus of the electronegative antimony as antimonic acid over and above the amount necessary to form a normal antimonate with the electropositive metals present. Calculating on the basis of the atomic weight of Sb 120, monimolite agrees very fairly with the formula (R'O). Sb2O5, or RSb2O,; Romeite comes nearest to (R'O) (Sb2O3)3. (Sb2O5)2, or R'Sb"SbyO (Dana makes this (R"O). Sb2O. Sb2O; ammiolite of Domeyko agrees best with (CuO),. Sb2O5, or CugSb2Og, while Rivot's analysis of a similar mineral from Chili comes fairly near (CuO),. (Sb2O3)3. (Sb2O5), or Cu,Sbg''Sby016 (which may perhaps mean (CuO),. Sb2O ̧ . Sb2O5, corresponding to Dana's formula for Romeite); while in Bindheimite the atomic ratio of PbO: Sb2O, derived from the analyses recorded, ranges from 1:1 to 2:1, even assuming that we have here a hydrous salt instead of a mixture of antimonic acid with one of more strongly basic character. I propose to name this mineral Bárcenite (accented on the first syllable) in remembrance of the worthy Mexican gentleman from whom I received it; his scientific work and zeal for scientific progress are honorable to himself and to his country. University of Virginia, August 13, 1878. * Volgerite was described as a natural antimony ocher having this composition. Dana remarks (Mineralogy, p. 188), that the only published analysis, by Cumenge, on material from Constantine, Algeria, corresponds to Sb2O. 4H,O. By my calculation Cumenge's figures lead rather to Sb2O,. 3H,0, or Sb2O,. Sb2O5. 6H2O. ART. XXXVI.--On the Intra Mercurial Planets; by Professor J. C. WATSON; from letters to the editors, dated Ann Arbor, Sept. 3d, 5th and 17th, 1878. ANN ARBOR, Sept. 3, 1878. THE places of the two objects observed by me during the total eclipse of July 29, as communicated in my letter of Aug. 13, were derived from hurried readings of the circles made immediately after my return from the eclipse expedition, in order to be able to answer numerous inquiries addressed to me for more precise information in regard to the observations than had been published in the newspapers. I have since made a more careful determination. When I came to examine the adjustment of the hour circle to be read upon the reading circle, I noticed that there was a very considerable error of eccentricity, which was shown upon revolving the alidade. Having attended to the adjustment for parallelism of the two circles, I did not attempt to change the eccentricity error, since there would be an error of this kind to be determined in changing the hour circle from the instrument to the reading circle, and since the corrections to be applied on account of the eccentricity can be determined from the four pointings on the sun. I have made ten readings upon each mark, backward and forward, so that each reading is an independent determination, and the results derived from the mean of these readings are shown by the following: By comparing the mean of the second and third readings upon the sun with the two extreme readings, I have obtained the following expression for the correction for eccentricity: These give the following differences in right ascension between (a) and (b) and the sun : and using the differences of declination as already given, we obtain the following results: Washington M. T. Object. h. m. 8. (a) Planet- h. m. 8. -0° 22' 8 27 24 +18° 16' -0 35 8 9 24 +18 3 1878, July 29. 5 16 37 "L 29. 5 17 46 (b) As already stated in my letter of Aug. 13, there is no uncertainty in the place of (a) beyond the unavoidable instrumental error, which is very small. I saw both it and ℗ Cancri, and it was fully a magnitude brighter than the latter. In regard to (b) it is possible but not probable that the pointing of the instrument may have been disturbed by the wind. I marked the position on the hour circle first, and but a moment was occupied in passing from the eye piece to the hour circle. I believe that this observation can be relied upon as giving the place of a second intra-mercurial planet. ANN ARBOR, Sept. 5, 1878. In Professor Young's note upon the recent eclipse published in this Journal, p. 242, he states, in speaking of the discovery of Vulcan, that Professors Newcomb, Wheeler, Holden and others went over the same ground and found nothing, and the inference is made that they obtained negative evidence of some value to dispute the discovery announced. As to the nature of this negative evidence Professor Young is under a mistaken impression. I happened to be observing near Professor Newcomb and I was informed by him, at the close of the totality of the eclipse, that he had searched north of the sun. Hence he could not see the objects which I observed. I have seen Professor Holden since his observations were made and he told me that he had been misled in his preparations by having had the idea from the statements of others, who had observed total eclipses, that the illumination of the sky would be very much less than it really was, so that he had observed with optical power insufficient for a search under these circumstances. He used a hand comet-seeker of two and a half inches aperture, with a field of five and a half degrees, and he swept twice over a space thirty degrees in length and AM. JOUR. SCI.-THIRD SERIES, VOL. XVI, No. 94.–Oct., 1878. ten degrees in breadth. He did not see any stars until he swept out to Mars and Regulus. Professor Hall told me that he had searched north of the sun, but that his assistant Mr. Wheeler had searched south. He said, however, that they had been compelled to use a very high magnifying power. Any one who has tried to find so bright an object as Jupiter by attempting to direct the telescope, with a high power, without using the finder, will know how uncertain a search would be under the circumstances named. As to what was done by other observers I have no direct information. Mr. Swift's account of his work, as published in the New York Tribune, furnishes important corroborative evidence. But the records of my circles cannot be impeached by all the negative evidence in the world. There are no known stars in the places which they give, and hence I cannot be mistaken as to the identity of the objects which I observed. While referring to the subject of negative evidence, I might as well state here what my own observations give in this respect. Between the limits: Right ascension 8h 5m to 9h 5m, and declination +17° 30′ to +19°, I swept once forward and once backward, carefully, and I felt certain that the only objects besides known stars, down to the seventh magnitude inclusive, were the two whose positions I recorded on my circles. I conducted the search expeditiously, but with great care, keeping the motion of the telescope uniform; and if I were to repeat the observations I would not vary the method which I adopted nor undertake to examine a region of greater extent in the same period of time. I cannot conceive of a surer method of recording the position of an object observed, under the circumstances of these observations, without danger of mistake. ANN ARBOR, Sept. 17, 1878. Since the letters of Sept. 3d and 5th were written, I have received information from Professor Newcomb, Commander Sampson, U.S.N., and Lieutenant Bowman, U.S.N., who were observing near me, that goes to show that it is highly improbable that there could have been any disturbance of the pointing of my instrument on (b), which, for the reasons stated in my letter of August 13, was not verified, in this instance, after the circles had been marked, and which fact it was proper to mention in order that every circumstance connected with these observations might be known to astronomers. My telescope was more completely sheltered than any of the others at the same station, and all three of these observers state that there was no disturbance of their instruments at the time when these observations were made. I find, too, that the direction of the wind was such that its force, whatever it might have been, was directed almost wholly upon the motion in declination, which was securely clamped. And besides, I have made experiments with the telescope used in the observations, clamped the same as it was then, and I find that it would require a much greater force than if it had been fully exposed to the wind to change the pointing in the least degree sensible. I have also lately examined (Sept. 15), with the same telescope and magnifying power used in the eclipse observations, the stars in this part of Cancer, with the moon in the western sky and the bright twilight in the east, so as to obtain as nearly as possible the conditions of sky-illumination which existed at the time of the eclipse. I have a very distinct recollection in respect to the brilliancy of the stars which I saw, and by observing when the approaching daylight had reduced the light of certain stars which were east of the sun at the time of the total eclipse, so as to be just visible in the telescope as they were then, I have been enabled to form a still more definite opinion of the relative brilliancy of Cancri, the two new objects which I observed, and Cancri. The fainter of the two planets, that near Cancri, was certainly brighter than Cancri, and much more than a magnitude brighter than its neighboring star. ART. XXXVII.-Letter from Mr. Lewis Swift, relating to the discovery of Intra-Mercurial Planets. (Communicated to this Journal by Admiral JOHN RODGERS, United States Naval Observatory, Washington, D. C.) ROCHESTER, N. Y., Aug. 5th, 1878. BEFORE preparing a report of my observations of the total eclipse of July 29th, as observed at Denver, I hasten to lay before you the facts in detail of my supposed discovery of an intra-Mercurial planet. Having a comet eye-piece which far surpasses all others that have ever come under my notice, I, before leaving home, decided to devote two minutes of totality to searching for the hypothetical Vulcan. It gives, with my four and a half achromatic, a power of twenty-five, and has a field of 1° 30', flat and sharp to the edge. About one minute after totality I observed two stars by estimation 3° southwest of the sun, pointing toward the sun, of about the fifth magnitude, or what I estimated at the time, as bright through the telescope as Polaris is to the naked eye. How much allowance ought to be made in estimating magnitudes so close to a totally eclipsed |