of the outer lip, and within has the clouds of iridescent colors remarkably small and numerous, while in H. rufescens they are remarkably large. It is more ponderous than any Haliotis which we have seen, weighing 2 lbs. 2 oz. avoirdupois.

Zoological Museum, Amherst College. Hab. —?

Not finding this species in Reeve's very complete and excellent monograph, I have ventured to describe it as new.

IV. ASTRONOMY.

1. Lord Rosse's Telescope, (Lond. Athenæum, April 8.)-At the meeting of the Dublin Royal Academy, March 17, 1848, Dr. Robinson gave an account of the present condition of Lord Rosse's telescope. Dr. R. found that the speculum (whose figure, as he had formerly stated, was not quite perfect) as well as a duplicate one, had been polished by the workmen; and as he apprehended no difficulty in the process, it was repeated. An unexpected difficulty however occurred, which made much delay, till Lord Rosse discovered the cause. The success of the operation requires that it be performed at the temperature of 55°. In winter this must be obtained by artificial heat,-which however increases the dryness of the air, so that the polishing material cannot be kept on the speculum. In this case the surface is untrue, and gives a confused image. This was verified by the hygrometer, and remedied by a jet of steam so regulated as to keep the air saturated with moisture. The result was immediate; and at the first trial the speculum acted so well, that it was unnecessary to try any further experiments. Three additions had been made to the telescope: 1. The movement in right ascension is given from the ground by machinery intended to be connected with a clock movement which is in progress. 2. To obviate the difficulty of finding objects, an eye-piece of large field and peculiar construction is connected with a slide, so that it can be replaced by the usual one in an instant. It magnifies 208 times, and employs nearly four feet of the speculum, the same as Herschel's 40-feet; thus giving the power of trying what that instrument might show. 3. The micrometer is peculiar,-a plate of parallel glass, with a position-circle attached. Light admitted at its edge cannot escape at the parallel surfaces except they be scratched, and a scale of equal parts engraved on one of them with a diamond-luminous in a field absolutely black. The exceedingly unfavorable state of the weather subsequently prevented much from being done; in fact, there was but one good night, the 11th ult. In the moon he observed the large flat bot tom of the crater covered with fragments, and satisfied himself that one of the bright stripes which have been often discussed, had no visible elevation above the general surface. In the belts of Jupiter, streaks like those of Pyrrhus's cloud were seen; and the fading of their brown color towards the edge, is evidence that they are seen through a considerable and imperfectly transparent atmosphere. A similar shade in the polar regions, where little cloud is to be expected, seems to indicate that the brighter bands are cloudy regions, and the more dusky show the body of the planet. Several nebula were examined, and as formerly all were resolved. That of Orion is most remarkable. Even

before the mirror was perfect and in bad nights, the part of it which presents the strange flocculent appearance described by Sir John Herschel, is seen to be composed of stars, with the lowest power, 360. But Dr. Robinson's eye required 830 to bring out the smaller stars, amongst which these are scattered. Having seen them and known the easier parts, they were seen with the 3-feet and 500. **** Another interesting object is the planetary nebula, h. 464, situated in the splendid cluster, Messier 46, and probably a part of it. It is a disc of small stars uniformly distributed, and surrounded by the larger. Messier 64 is a singular modification of the annular form seen obliquely. The opening seems black as ink, and at its margin is one of those interior clusters of bright stars so often noticed before. But the most remarkable nebular arrangement which this instrument has revealed, is that where the stars are grouped in spirals. Lord Rosse described one of them (Messier 51) in the year 1845; and Dr. Robinson found four others on the 11th, of which he exhibited drawings, h. 604 (seen by Herschel as a bi-central nebula), Messier 99, in which the centre is a cluster of stars. Messier 97 looks with the finding eye-piece like a fig. ure 8, but the higher powers show star-spirals related to two centres, appearing like stars with dark spaces around them, though probably high powers in a fine night would prove them to be clusters. Another fact deserves to be noted from its bearing on Struve's Etudes d'Astronomie Stellaire. In that admirable book, among other curious matters, he infers that the eighteen-inch telescope of Herschel penetrated into space only one-third of what was due to its optical power. He explains this by supposing the heavenly spaces imperfectly transparent. In computing the limit, however, he assumes that the Milky Way is in its greatest extent "unfathomable by the telescope." Dr. R. however chanced to observe it when it is deepest at 6-4, and is certain that its remotest stars were very far indeed within the limit of the six-feet, and very much larger than those of the nebula of Orion.

2. New Planet, (Lond. Athenæum, May 6, 1848.)-A new planet was discovered by Mr. Graham, at Markree, Ireland, April 25, 1848. It appeared like a star of the tenth magnitude; R.A. 14h 55m, S. declination 12° 32'; daily motion in R.A. Im 7s retrograde. It is supposed to belong to the group between Mars and Jupiter.

3. Supposed new Star, (ibid.)-A new star of the fifth magnitude in the constellation Ophiuchus, was noticed at Mr. Bishop's Observatory, London, April 28, 1848. No star has been previously recorded in the position of this. It is in a line joining eta and 20 Ophiuchi, rather nearer to the latter; R.A. 16h 51m 18, S. decl. 12° 39'. It is some degrees distant from the place of the famous object seen by Kepler in 1604.

4. On the opinion of Copernicus with respect to the Light of the Planets; by Prof. DE MORGAN, (Phil. Mag., xxxi, p. 528.)—The common story is, that Copernicus, on being opposed by the argument that Mercury and Venus did not show phases, answered that the phases would be discovered some day. The first place in which I find this story is in Keill's Lectures. It is also given by Dr. Smith, in his wellknown Treatise on Optics, by Bailli, and by others. But I cannot find it mentioned either by Melchoir Adam or Gassendil, in their biographies of

Copernicus; nor by Rheticus, in his celebrated Narratio, descriptive of the system of Copernicus; nor by Kepler, nor by Riccioli, in their collections of arguments for and against the heliocentric theory; nor by Galileo, when announcing and commenting on the discovery of the phases; and, what is most to the purpose, Müler, in his excellent edition of the great work of Copernicus, when referring to the discovery of the phases of Venus, as made since, and unknown to, Copernicus, does not say a word on any prediction or opinion of the latter.

This story may then be rejected, as the gossip of a time posterior to Copernicus. If we try to examine what the opinion of Copernicus on this matter really was, a point of some little curiosity arises. It depends on one word, whether he did or did not assert his belief in one or other of these two opinions,-that the planets shine by their own light, or that they are saturated by the solar light, which, as it were soaks through them. I support the affirmative: that is to say, I hold it sufficiently certain that Copernicus did express himself to the effect that one or the other of these suppositions was the truth.

If we take the first edition of the work De Revolutionibus, which was printed from the manuscript furnished by Copernicus himself, there is little doubt about the matter. There are but two passages which bear or can bear upon the question. The first is in the ad lectorem, in which the writer (Osiander, though even Delambre make him Copernicus) asks whether any one acquainted with geometry or optics can receive the Ptolemaic epicycle then used to explain the motion in longitude of Venus? But the meaning of the allusion to optics is explained in the next sentence, by a reference (and by no means a fortunate one) to the changes of apparent diameter of Venus derived from the epicycle; changes which, as they made the perigean diameter more than four times as great as the apogean, were assured to be falsified by common experience. The second passage is the one on which this discussion must turn. In book i, chap. x, after noting that some had heretofore believed Mercury and Venus to come between the earth and sun, he mentions the difficulty arising from the absence of the remarkable phase, which we now call the transit over the sun's disc. He describes the opinion just mentioned favorably, referring, not to his own view, but to that of those others who had held it. This is not an uncommon idiom: persons advocating an unpopular opinion are very apt to describe the maintainers of it in the third person, though themselves be of the number. But when he comes to describe what he takes to be the necessary consequences of the opinion, he lapses into the first person as follows:"Non ergo fatemur in stellis opacitatem esse aliquam lunari similem, sed vel proprio lumine, vel solari totis imbutas corporibus fulgere, et idcirco solem non impediri...

That

These are the words of the first edition (Nuremberg, 1543). Copernicus could have answered any objection, either by word or writing, is impossible, since he drew his last breath within a few hours of the time when, not able to open it from weakness, he saw the first printed copy. The second edition (Basle, 1566) is usually said to have been edited by Rheticus. The reason of this is that the name of Rheticus appears in the title-page. But this appearance only arises from the Narratio, &c. of Rheticus being added to the edition; and it is

only the description of this edition which brings Rheticus into the title. page. There is no mark whatever of his having been the editor; and as the work was printed at Basle, where I cannot find that Rheticus ever sojourned, and as the latter was deeply engaged at the time in his enormous trigonometrical calculation, some proof of his editorship must be given before it is admitted. As the point is of importance, I will notice, that unless Rheticus had made some stay at Basle, it is very unlikely he should have edited a work printed there. He did not edit the first edition, only because it was found convenient to print it at Nuremberg instead of at Wittemberg; and it was accordingly entrusted to Osiander. Now, if ever there were a connexion between two men, and between one of them and the book of the other, which made it desirable and even necessary that the first should edit the second, it was the case of Rheticus and the first edition of the De Revolutionibus, &c.; and yet no arrangement could be made by which the sheets printed at Nuremberg could be revised at Wittemberg. It is very unlikely, then, that Rheticus should have edited the second edition, when, as far as we know, a similar impediment existed.

The third edition by Müler (Amsterdam, 1617), has no authority as to the text above that of the second.

Now both the second and third editions change the word fatemur into fatentur, thus causing Copernicus to throw the opinion in question upon his predecessors, instead of directly making it his own. Not that it would be conclusive, even if the emendation were adopted: for, as I have said, Copernicus is evidently speaking with approbation of the opinions which he describes; and it would be difficult to say why comperiunt or putant in one sentence should imply approbation, and fatentur, in the next, should be at least disavowal, if not disapprobation. If Rheticus, who knew the mind of Copernicus better than any one, had been the editor, I can conceive that stress ought to be laid upon the change of the first into the third person as an emendation; that is, I should be somewhat staggered by Rheticus having thought it necessary to make such an alteration.

But, Rheticus not being in the question, as I think, for the reasons given above, the next best authority on an opinion of Copernicus is Galileo. Now the latter, in speaking of the phases of Venus, expressly attributes to Copernicus the maintenance of one of the two alternatives, -that the planet is either self-luminous or perforated by the solar rays. Of these alternatives, he says, in his letter to Velser (Works, vol. ii, pp. 88, 89), "Al Copernico medesimo convien amettere come possibile, anzi pur come necessaria una delle dette posizioni." And that such was the opinion of Copernicus is also assumed by the writer of the note on the Sydereus Nuncius in the volume just mentioned, and by others, even down to our own time; as by Mr. Drinkwater Bethune, in his life of Galileo. In fact, with the exception of the unsupported story mentioned at the beginning of this paper, there is nowhere, that I can find, any thing against my conclusion. And it is to be remembered, that Copernicus nowhere shows any of that acumen in matters of physics, apart from mathematics, which has often enabled the cultivators of the former to make steps more than proportionate to their knowledge of the latter. Ptolemy, the great promotor of the old theory, and Coper

nicus, its destroyer, were both mathematicians in a peculiar sense; Ptol. emy being far the more sagacious in questions of pure experiment. Their grounds of confidence are mathematical; and Copernicus, in particular, dares to face his own physics (for there is no reason to suppose he was beyond his age in mechanical philosophy) with reasons drawn entirely from probabilities afforded by mathematics.

There is much reason to regret the practice of associating with the names of those who have led the way in great discovery the glory which is due to their followers. The disadvantage is twofold. In the first place, it introduces into the history of science an index error of from one to two centuries; secondly, those who come to inquire are disappointed to find that they must lower their opinion of great men, and are perhaps led to do it to a greater extent than justice requires. Our usual popular treatises speak of Copernicus as if, besides himself, he had in him no inconsiderable fraction of Kepler, Galileo, Newton and Halley. What is a person to think who comes from these histories to actual investigation, when he finds in Copernicus himself the immovable centrum mundi (only reading sun for earth) of the Ptolemaists, their epicycles, and a suspicion, at least, of the solid orbs?

5. Solar Parallax.-A Report was submitted to Congress in April last, with reference to setting on foot an expedition to the most southern available position on the western Continent, for the purpose of making observations on the planet Venus during the period of her retrograde motion: these observations are to be conjoined with similar observations at the Observatory in Washington city, with a view to determining, more accurately than has hitherto been done, the solar parallax. The plan emanated from Dr. Gerling of Marburg, well known for his astronomical and geodetical labors, and was communicated by him in a letter to Lieut. Gilliss, dated April 17, 1847, in which he earnestly seeks for the cooperation of American astronomers. The correspondence on the subject between Dr. Gerling and Lieut. Gilliss, addressed by the latter to the Chairman of the Committee of Naval Affairs of the House of Representatives, was made the basis of the Report. The object is one worthy of a national expedition. The Report states that in 1769, Dr. Rittenhouse, under the patronage of the government of Pennsylvania, made observations on the transit of Venus that were of great value. The subject is therefore already connected with the history of American science, under the auspices of government patronage.

V. MISCELLANEOUS INTELLIGENCE.

1. Memoire sur les Temperatures de la Mer Glaciale à la surface, à de grandes profondeurs, et dans le voisinage des Glaciers du Spitzberg; par CH. MARTINS, Membre de la Commission Scientifique du Nord. (Extrait des Voyages en Scandinavie, en Laponie, et au Spitzberg de la Corvette la Recherche, Geographie Physique, ii, 279. Paris, 1848.-The following are the results of these valuable researches, as laid down by the author. They relate to the temperature of the sea near the icebergs in the two bays of Spitzberg.

1. In the month of July and August, the surface temperature, although very near the freezing point, is always above it.