reading off the measure by means of an achromatic microscope, on the stage of which it is placed. One of the webs is brought to the intersection cross-wires in the eye-piece of the microscope; and by turning a screw (the revolutions of which are counted), the frame travels before the microscope, and the other web is brought to the intersection of the cross-wires. The parts of a revolution are read off by a vernier from a large divided circle attached to the screw. The advantages arising from the peculiar construction of this micrometer are the following: 1. Distances can be observed with great accuracy up to about one degree, and the angles of position also. 2. The webs, being in the same plane, are free from parallax, and are both equally distinct, however high the magnifying power may be. 3. The webs are also free from distortion and from color. 4. A different magnifying power may be used on each of the objects; which may be advantageous in comparing a faint comet with a star. 3. New Double Stars discovered by Mr. Alvan Clark; communicated by the Rev. W. R. DAWES. (From Monthly Notices of the Royal Astronomical Society, xx., p. 55. Second series.) All the double stars in this series may be considered as good testobjects for telescopes of from 6 to 8 or 9 inches aperture. But it is not merely as such that they are interesting: they become especially so from the fact that they are all situated in the northern hemisphere, and all but one at more than 30° from the equator. They consequently attain a good altitude at Pulkova; notwithstanding which they have escaped the acute search of M. Otto Struve with the 15-inch refractor, in addition to the previous one by his father with the Dorpat telescope of 9.6 inches aperture. Either, therefore, they have recently undergone considerable change; or, if not, it appears that objects of great difficulty and delicacy may be detected with very perfect telescopes of smaller size, which have escaped the most diligent scrutiny with far larger instruments. The whole of these objects were discovered by Mr. Clark with his own object-glasses of 8 and 8 inches aperture, and five of them in my own observatory, during his visit to me last summer; since which I have met with seven others, of similar character and situation; and it should be mentioned that none of the objects recorded are below Struve's eighth magnitude for the larger star; all smaller, of which many have been found, having been systematically rejected. It appears, therefore, that there is still much oc SECOND SERIES, VOL. XXIX, No. 86.-MARCH, 1860. cupation for telescopes of moderate dimensions, even in this department of astronomy, which might reasonably have been supposed to have been long since exhausted. The distances stated in the list are from my own recent measurements. Haddenham, Thame, November, 1859. 4. Notice of the Meteor of Nov. 15, 1859; by Prof. E. LOOMIS.-In the last No. of this Journal, p. 137, I gave a brief notice of this meteor, but from want of space was compelled to limit myself to a brief summary of results. I have received a large amount of documents relating to this meteor, most of which however are too indefinite to be of much value. I now proceed to present a brief summary of what appear to me the most reliable observations. At New Haven, Ct., Judge W. W. Boardman saw the meteor descend at an angle of 25° to 35° with the vertical, and it passed from his view at the edge of the dome of a steeple in azimuth S. 35° 34' W. Continuing the meteor's path down to an altitude of 3° or 2°, we have S. 37° W. for the azimuth of the place where the meteor would have disappeared to him had his view been unobstructed. At New York city Mr. Tatham was riding in the Bowery, and saw the meteor descend at an angle of 20° with the vertical, and in a range with the middle of the street opposite the Old Bowery theatre. According to the map of the city, this direction was S. 27° W. The diameter of the meteor appeared to be about one-third that of the full moon. A correspondent of the Evening Post, walking down Broadway, saw the meteor disappear in azimuth S. 25° W. Mr. Gould, also in Broadway, saw the meteor disappear behind a building in azimuth S. 23° W. Mr. Pirsson, also in Broadway, saw the meteor disappear behind a high building in azimuth S. 21° W. Mr. Bradley, also in Broadway, reports that the meteor disappeared in azimuth S. 16° W. Several other observers agree as to the general direction of the meteor, but their statements are less precise than those of the preceding. As Mr. Bradley's observation differs materially from the others, I reject it, presuming that his memory must have been in fault, either in respect to his point of observation, or that of the meteor's disappearance. The mean of the other four estimates is S. 244° W., or allowing for the effect of the high buildings which obstructed the view of three of the observers, the mean would be about S. 26° W. This result differs five degrees from my former estimate; a difference which is explained by my having obtained two new observations, and by my rejection of Mr. Bradley's observation. At Washington, the apparent path of the meteor was vertical, and its point of disappearance was estimated at four degrees north of east. A gentleman four miles west of Dover, Del., was riding towards Dover. His wife saw the meteor; he only saw the smoky trail which he describes as a nearly vertical column, with its base 20°, and its top 40° from the horizon; direction due east. Mr. Parsons, at Salisbury, Somerset county, Md., saw the meteor descend in a slanting direction to the earth, when it exploded with a dull sound. Its direction was from the N.E. At Lewistown, Del., the meteor was seen to fall in the N.E. The report was heard five minutes later-loud but distant. If we mark upon a map all the preceding directions, we find that the lines do not intersect at one point, but they indicate the most probable point of the meteor's disappearance to have been near lat. 39° 10′ and long. 75° 5'. At New Haven, the path of the meteor was estimated to make an angle of from 25° to 35° with the vertical. Mr. Wilder Smith, near Waterbury, Ct., estimated the inclination to the vertical at about 30°. At New York, Mr. Tatham estimated the angle with the vertical at 20°, Mr. Gould 10°, Mr. Pirsson 35°, and Mr. Bradley 45°. The mean of these four estimates is 27°. At Washington, the path was pronounced exactly vertical. The actual path of the meteor was therefore such as, if continued, must undoubtedly have struck the earth. It must have passed vertically over the extreme southern part of New Jersey, and must have struck the earth in Delaware Bay, or near its shore. That this conclusion is a near approximation to the truth, is confirmed by observations from the southern part of New Jersey. Mr. Mills was surveying in the forest four miles west of Stephens Creek in Atlantic county, and heard a noise nearly overhead. He looked up and saw a cloud of a rounded form like a puff of smoke about 15 degrees south of the zenith. At Millville, Cumberland county, a strange rumbling noise was heard somewhat resembling thunder, and one or more clouds of smoke were seen in a southeast direction at an elevation very roughly estimated at 45°. At Newport, Cumberland county, a rumbling noise, which lasted two minutes, was heard in an east or southeast direction. At Maurice River Cove, Cumberland county, the captains of the oyster boats saw a flash and smoke in an easterly direction. At Dias Creek, Cape May county, Mr. Smith states that the noise was great and lasted two or three minutes. The flash was brilliant, and the smoke was seen in a northeast direction at an elevation of 75° or 80° above the horizon. At Goshen, Cape May county, a noise was heard in a northeast direction, and a cloud of a rounded form was seen in the northeast. At Dennisville, Cape May county, the noise appeared directly overhead. There was a small cloud or belt of white smoke left in the train of the meteor, about five degrees northwest of the zenith, the atmosphere being perfectly clear at the time. The detonations lasted somewhat over a minute. The directions indicated in the preceding notices have a decided convergence towards a point near lat. 39° 13', and long. 74° 52'. This result accords so nearly with that derived from observations made at a distance of a hundred miles and upwards, as to show that the observations are in the main reliable, but subject to that uncertainty which attends all estimates made without instruments, and not reduced immediately to writing. We must then conclude that this meteor passed vertically over the southern part of New Jersey, nearly on the parallel of 39° 13', and that it struck the earth near the eastern shore of Delaware Bay, probably between Dennis Creek and Maurice River. I assume that this meteor was a solid body. We are acquainted with two classes of meteors quite distinct from each other and differing greatly in density. Ordinary shooting stars have never been known to reach the earth's surface, or to produce any audible noise. Another class of meteors like that of Agram in 1751 is composed chiefly of iron, and another like that of Weston, Ct. (1807), partly of iron and partly of silicates. They frequently strike the earth, or at least let fall fragments to the earth, and are attended not only by a brilliant flash of light, but by a tremendous noise. The New Jersey meteor bore a striking resemblance to the Weston meteor, not only in the brilliancy of its light, but in the noise which attended it. We cannot doubt that it was a body of considerable density; and the direction of its motion was such that the entire mass must have struck the earth. It may have sunk into Delaware Bay and not a single fragment have fallen upon dry land; but there is reason to hope that at least some fragments of it may yet be discovered. Such fragments, if they exist, are probably scattered along an east and west line coinciding nearly with the parallel of 39° 13', and the entire mass probably lies near the meridian of 75°. 5. Sandwich Island Meteor of Nov. 14, 1859.-A meteor of remarkable size and brilliancy was seen from the slope of Mauna Kea north of the great volcanoe of Kilauea, S. I., soon after dark of the 14th November last, shaped like a cross, having the light of the moon at full, moving vertically south from a point a little below the zenith and disappearing near the crater.-Pacific Com. Advertiser, Dec. 15. 6. Der Meteoreisenfall von Hraschina bei Agram am 26 Mai 1751; von W. HAIDINGER. Wien, 1859.-Prof. Haidinger has here revised all the contemporary evidence respecting the fall of this remarkable meteoric iron mass, the details of which are fortunately well authenticated. This history is of great interest at the present moment when the late meteors of August and November last have called up anew the discussion of this subject. V. MISCELLANEOUS SCIENTIFIC INTELLIGENCE. 1. Monthly varying level of Lake Ontario, measured, in inches, from a fixed point above the surface downwards, for fourteen years, at Charlotte, mouth of Genesee River, N. Y.: Year. Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec Mean Range. Low. 35.8 23 Higher. 41.3 25 Lower. 42.7 19 do. 41.9 26 do. 45.0 19 Low. 34.7 29 Higher. 27.8 1. As more water falls usually in the warmer months, the Lake is higher in those months generally than in the colder months. 2. The range has been only 54 inches, the lowest being in February, 1857, and the highest in August, 1858, and in June, 1359; the mean of the two is 27 inches. 3. In 1846 and 1857 the mean level lowest, and in 1858 and 1859 highest. 4. In 1853 the Lake was near the mean level, and in 1857 only a little less, though the first half of the year gave low water and the last half high. 5. The Lake was near the highest, or within four inches of it, in May, June, July and August, 1858, and in May and June, 1859, and of course the average of both years was high. 6. The Lake down to 50 inches or more in January and February, 1846; in November and December, 1848; in January, February and March, 1849; in October and November, 1850; in February, November and December, 1851; in January and February, 1852; in December, 1854; in January and February, 1855; in November and December, 1856; and in January and February, 1857. These statements show that the changes of the level must be owing to the ordinary causes of supply or diminution of water over this great watershed, and disprove any notion of periodic rise and fall under any but meteoric laws. As the water was high in the Lake through 1858, it was suggested that the average fall of water must continue it high in 1859, as the measures now prove. In November, 1859, the water fell to the mean, and rose afterwards from the great autumnal rains at the west which had flowed into Lake Ontario. C. D. 2. Eruption of Mauna Loa, Sandwich Islands, (in a letter to Prof. DANA from Prof. R. C. HASKELL, Oahu College, dated Honolulu, Nov. 5, 1859). Since my last dates (June 22d)* the lava continues to flow from the place of the recent eruption. With scarcely any cessation since the middle of June it has been flowing into the sea. Hawaii has been increased in area by many acres at least, by several hundred acres it is said. After writing you from Kona in June, I visited Kilauea, which I found very quiet. There has, however, been considerable action since you were there in 1840, for the crater is now filled up even with the "black ledge" of which Wilkes speaks. From Kilauea, passing through Hilo, I went to Waimeu, intending to ascend Mauna Kea, but the weather proved so rainy and foggy that I was unable to do so. From Waimeu I went direct to Kona, crossing the lava stream without difficulty on a mule, between the three mountains. The stream was fully three miles wide where I crossed, and at some points above appeared to be five or six miles wide. At this time the lava was flowing into the sea, and of course running under me as I crossed, yet the lava on the surface was in no place so hot as to burn the hoofs of the mule, or even to be noticed by myself, unless I touched my hand to it. After arriving at Kona I went by canoe to visit the place where the lava was then and is still flowing into the sea. Without attempting to give an adequate description of the sight presented as I passed, by night, a few rods in front of the stream, which was more than a mile wide, I will only mention one fact. * Vol. xxviii, [2], 284. |