and for more than thirty years our young professional men, naturalists, and others who have visited Europe, have experienced cordial welcome and thoughtful kindness at his hands. The following gives a good idea of the man "When practising as a physician he discarded the customary black coat, knee-breeches, and silk stockings, for the very good reason that sombre colors could not but suggest gloomy ideas to the sick; and he was one of the first who adopted the custom, now universal in the profession, of dressing in ordinary costume. In doing this Dr. Boott adopted the blue coat, gilt buttons, and buff vest of the period, which he continued to wear to the last, and with which dress his casual acquaintance, no less than his personal friends, will ever associate him. In person he was so tall and thin as almost to suggest ill-health; and the refinement of his manners, his expression, address, and bearing were in perfeet keeping with his polished mind and many accomplishments." The preceding extracts are all from an excellent article in the Gardener's Chronicle for January 16, to which we are much indebted. In the first volume of the late Dr. Wallich's splendid Planta Asiatica Rariores, published in the year 1830, is the figure of a handsome and curious Butomaceous plant, BOOTTIA CORDATA, a genus dedicated "in honorem Francisci Boott, Americani, botanici ardentissimi et peritissimi, amici dilectissimi, non minus animi probitate quam scientiarum cultu, et morum suavitate egregii." A. G. Jacques Gay. We have just heard of the death of this excellent man and botanist, but without details. The event must have been sudden, as we had news of him almost down to the close of the year. He was born in Switzerland, was a pupil of Gaudin, who bequeathed to M. Gay his herbarium; but most of his years, which were little under fourscore, were passed in Paris. The weekly réunion of botanists in his modest apartments at the Petit Luxembourg, which has continued through a long life-time, is now done away; and to botanists Paris will seem other than it was, without him. V. ASTRONOMY. A. G. 1. Comet IV, 1863.-This comet was discovered by M. Tempel at Marseilles on Nov. 5th. It was visible to the naked eye, shining as bright as a star of the 5th magnitude. It appeared as a condensated nebula, showing a tail about 2° long. The following elements were computed by Mr. H. Romberg. T1863, Nov. 9.49923, Greenwich m. t. i = 78 6 46 5 log. q = 9.849148 Motion direct. This comet was seen during November and December by several persons in this country, having been visible to the naked eye, and by some was confounded with the comet discovered by Prof. Watson Jan. 9th. 2. Comet V, 1863.-This comet was discovered on Oct. 9th by Mr. Bäcker at Nauen. The following elements were computed by Mr. Hermann Romberg. T 1863, Dec. 27.70863, Greenwich m. t. 104 51 28 8 2= 82 16 29 .4 log. q= 0.131934 Motion direct. } Apparent equinox of Oct. 14.5. This comet appeared as an oblong nebula, strongly condensed in the middle. Its diameter was about 1, and it shone as a star of the 8th magnitude. 3. Comet VI, 1863.-On the 28th of December, 1863, M. Respighi, Director of the Observatory at Bologna discovered a new comet (the sixth of 1863). It exhibited a nebulosity condensed toward the centre, with the trace of a tail about half a degree in length. The following are two observations of Dec. 28th. m. t. Bologna. R. A. 18 11 2 18 50 1.76 Dec. 26 13 2.2 M. E. Weiss has calculated the following elements of this comet. M. Weiss remarks that these elements resemble those of the comets of 1490 and 1810, the three perihelia being separated by intervals of 53 years, and of 320-6X53 years. This comet was discovered at Ann Arbor on the 9th of January, as announced in the following letter from Prof. Watson: AM. JOUR. SCI.-SECOND SERIES, VOL. XXXVII, No. 110.-MARCH, 1864. GENTLEMEN: "Observatory, Ann Arbor, Michigan, 1864, Jan. 18. I have the pleasure to inform you that I discovered a new comet on the evening of Saturday, Jan. 9th, at 6 o'clock. I have observed the following accurate positions: 12, Comet d. +34° 6' 5"-9 34 52 52 -2 35 42 47 0 From these places I have derived the following elements of the orbit: T-1863, Dec. 27-1413 Washington M. T. 8=304 40 49 0 App. equinox, Jan. 11th. i 63 55 38 5 log q = 9.885810 Motion direct. The comparison of the middle place gives: C.-O. Al cos B-29 AB=-15"0 The comet is large and bright, with a tail 14° in length, and a nucleus strongly condensed at the centre. The above elements almost exactly resemble those of the comet of 1810, so that there can be very little doubt of the identity of the two comets. Whether this is the first return to the perihelion since 1810, or whether it has returned several times unperceived, must be decided by subsequent observations. Very truly yours, JAMES C. WATSON." This comet was barely visible to the naked eye during the latter part of January, and in a comet-seeker exhibited a tail about 2° in length. 4. Notes on n Argus; by F. ABBOTT, Esq. (from Proceedings Royal Astronomical Society, Nov. 13, 1863.)-That the duration of this star's apparition is variable to a great extent is certain; and by comparing the present description with the monograph of Sir J. Herschel, taken at Cape of Good Hope, it will, I think, appear conclusive that the apparition of the surrounding nebulæ is also variable. Messier recommended careful observations to be made on such objects, with a view to ascertain whether or not any indications of change in form or structure are exhibited. That such changes have taken place is already on record. An instance is afforded by the remarkable nebula surrounding in the constellation of Orion, which Huyghens discovered in 1656, and noted in his Systema Saturnium; from comparison of which Sir Wm. Herschel, by his own observations from 1783 to 1811, concluded it had undergone sensible change. Bouillard and Le Gentel maintained the same opinion in reference to the nebulæ in Andromeda ; and of later date, Bond, Pogson, Struve, D'Arrest, and others, have observed such changes. Sir John Herschel, when at the Cape, carefully examined ʼn Argus with an 18-inch reflector; "No part of this nebula," says Herschel, "shows any sign of resolution into stars." "It is not easy," he adds, "for language to convey a full impression of the beauty and sublimity of the spectacle which the nebula offers as it enters the field of the telescope." "It will appear," he also writes, "that every succeeding state of nebulous matter is the result of the action of gravitation, and by such steps the successive condensation of it is brought to a planetary or stellar condition. Several instances are on record which connect the planetary with the stellar appearance. In those instances wherein the collection of nebulous matter was very extensive, subordinate centres of attraction could not fail to be established, around which the adjacent particles would arrange themselves, and thus the whole mass would, in process of time, be transformed into a determinate number of discrete bodies, which would ultimately assume the condition of a cluster of stars." That this condition is partly carried out in the object ʼn Argus will be manifest by comparing the Cape description with the present one. A great difference may be caused by the optical means employed, as far as resolvability goes; but if an increased number of brilliant isolated stars, with a change in position of ʼn Argus, is the effect produced by a 5-foot achromatic, and they were not exhibited to the same effect in an 18-inch reflector, it only strengthens the evidence in favor of some change having taken place in the object. η OPEN NEBULA 納 The open space, as given in the Cape Monograph, and also in the last edition of the Outlines, is somewhat in the form of a dumb-bell, compressed in the centre and surrounded with nebulæ, in the most dense part of which is situated Argus. The appearance of the open space now assumes the form of a crooked billet, wide in the centre and open at both ends, with n Argus situated within the open space or dark part, and NEBULA OPEN surrounded with an almost innumerable quantity of brilliant stars, many of which are arranged in groups, some being of a blue, and some of a ruddy color. They are remarkably brilliant in the dark space, and afford a good comparison with the variable star itself. It appears somewhat paradoxical that in 1838, when examined by Sir J. Herschel, the star n Argus was situated in the most dense part of the nebula, and was seen as a star of the first magnitude. And now in 1863, it is out of the nebula, and, within the dark space, it appears only as a star of the sixth magnitude. That the star's right ascension has not varied so much will be manifest. It is clear then that the dense portion of the nebula, towards the east, must have receded, leaving each end open, and n Argus, together with about 70 stars up to the 14th magnitude, as seen within the dark space. The irregularity of this star, and the nebulosity surrounding it, involve a principle as to whether its accession and diminution is the effect produced by distance, transits of opaque bodies, or solar spots; or whether the nebulosity surrounding Argus interferes with the light emitted by the star; if so, the increase and diminution, however vacillating, become obvious. VI. MISCELLANEOUS SCIENTIFIC INTELLIGENCE. 1. Account of the casting of a gigantic (Rodman) Gun at Fort Pitt Foundry, (in a letter to the Editors, dated Pittsburgh, Penn., Feb. 1864.) -A 20-inch army gun on Rodman's plan, has lately been cast at the Fort Pitt Foundry in this city. Being the largest iron gun in the world, its manufacture necessarily awakened much interest here. Thinking therefore that your readers may feel a like interest, I take the liberty of sending you the facts of the casting, as well as the theory of this improved method. It has long been known that there is a practical limit to the manufacture of large iron guns, cast solid, beyond which the size cannot be increased. This arises from the method of cooling, which is entirely from the exterior. Of course the first part to become solid is this exterior surface. As the cooling progresses, and the solidification proceeds toward the centre, the iron coutracts and produces an enormous tension, acting in opposite directions-that is radially, in the cross section. A force of compression is felt on the exterior, to crush it inward; and one of radial elongation, exerted from within outward, on the interior, to tear it asunder. This condition of things in glass is well illustrated in the Prince Rupert's drop. In the case of solid cast iron shot, for example, there is a maximum diameter within which these can be cast without containing cavities. But beyond this point, the contraction toward the exterior, which is the first to solidify, is so great that these cavities are formed. In general the contraction is irregular and the cavities are near the upper surface. Hence it is considered preferable to cast thick shells, in which case the core locates the cavity exactly in the centre. For the same difficulties in casting large guns, it was at first proposed to apply the same remedy. That is, to cast the gun.with a core, so that the contraction should be uniform from the axis to the surface. Major-then Lieutenant-T. J. Rodman had his attention first called to the manufacture of guns of this sort, as he recently stated before the Committee on the conduct of the war,-from the lamentable accident which occurred on board the steam frigate Princeton, in 1844. The "Peacemaker" was a wrought iron imported gun, having a bore twelve inches in diameter. Considering the conditions under which iron guns were usually cast, Major Rodman at once saw the enormous strain to which they were subjected by exterior cooling. And he also perceived that a gun thus cast was in a state of extreme tension and therefore weak. He then applied himself to the mathematical investigation of the conditions under which a central force acts. He found that Barlow had determined that the strain produced upon any material by a central force, diminishes as the square of the distance from the centre increases. Thus in a gun one calibre thick the distance from the bore to the exterior is 3, and the strain on the exterior when fired is only 4th that on the interior. Now if the strain at the interior is the breaking strain, then this |