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Path of the Central Eclipse, or of the centre of the shadow of the Moon over the Earth, on Monday, July 28th, 1851.

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Greatest north latitude of the central path.
Duration of the central eclipse on the earth 2h. 14m. 61sec.
SECOND SERIES, Vol. XII, No. 34.—July, 1851.

18

** On the meridian of the place.

The beginning and end, &c. of the eclipse at the following places. are expressed in mean and civil time of each particular place. The angles of the points on the Sun's disc, at which the obscuration will begin and end are counted from the vertex or highest point of the Sun towards the right hand, as seen through a telescope that does not invert; for an astronomical telescope, 180 degrees should be added thereto.

The Sun will rise at Sitka and Port Stewart at 3h. 56m. and 4h. 3m. and will set at Tifflis at 7h. 20m. The obscuration at the Observatory at Cambridge will be on the northern, and at Sitka on the southern limb of the Sun.

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centres,

diff. S. D. 5343 diff. S. D. 53-28 diff. S. D. 5313

6'80 South

20/02

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At Carlscrona, lat. 56° 9' 31", lon. 15° 35′ 13′′ E., the apparent North latitude of the Moon at 4h. 15m. 35sec. will be 841, and the eclipse will be total from 4h. 13m. 51sec. to 4h. 17m. 16sec.

At Elsineur, lat. 56° 2′ 20′′, lon. 12° 37′ 30′′ E., the least distance of the centres (5384) will take place at 4h. 2m. 34sec., and as the difference of the semi-diameters is 54"-45, the eclipse by computation will be total there.

At Copenhagen, in lat. 55° 40′ 53", lon. 12° 34′ 57′′ E., the least distance (6528) will take place at 4h. 3m. Isec., and the magnitude of the obscuration will be 11° 56' on the north limb of the Sun.-Boston Daily Advertiser.

Boston, March 26th, 1851.

V. MISCELLANEOUS INTELLIGENCE.

1. Electro-magnetic Locomotive, (From the National Intelligencer of May 3, 1851.)-We lay before our readers a statement from Professor Page respecting the Electro-magnetic Locomotive; and when we regard the fact that the highest power ever attained before his experiments was less than half a horse power, and that costing probably one hundred times as much as it does under this new mode of its application, we cannot be indifferent to so great a result, and the high promises with which it seems to be fraught:

Messrs. Editors :-The electro-magnetic locomotive made a very favorable trip on Tuesday last, more especially when it is taken into the account that we were constrained to make this trial with only one

half (or even a little less,) of the power the engines and battery are capable of yielding. Each engine, calculated upon the basis of my stationary engine, ought to give at the lowest estimate 12 horse power, which would make the locomotive 24 horse power. The actual power I have not been able to ascertain; but the following data may serve to give some idea of its power. The locomotive, with the battery fully charged, weighs ten and a half tons. With the seven passengers taken on the trip to and from Bladensburg the weight was eleven tons. Under the most favorable arrangements eight pounds are required to start a ton on a perfectly level rail, and seven pounds will barely keep a ton in motion. Ordinarily, upon railroads the allowance is ten pounds to a ton, but this applies only to cars unincumbered by machinery. The friction of locomotive machinery renders its draught far greater, and can only be accurately ascertained by experiment in each case. The magnetic locomotive, the first of its kind ever made, is imperfect, and, from the newness and stiffness of all the work, it runs exceedingly hard. We will take 200 pounds, which is below its actual power required to keep it in motion on a level portion of the road. A horse power upon the usual estimate is 150 pounds 23 miles an hour, or 375 pounds 1 mile an hour. The speed of the magnetic locomotive is, we will say, 15 miles an hour on a level road, (it has in fact made more,) and its traction 200 pounds. We have then 375 pounds 1 mile an hour for one horse, and 200 pounds 15 miles an hour for the locomotive, which gives eight horse power. But the engine has more than this. It has greater power at a slow speed, and must have, by all reasonable estimates, twelve horse power; which, as I said before, is about one-half its proper capacity. One of the most serious defects arises from a want of insulation in the helices. After the engine was placed on the road it was found neccessary to throw out of action five of the helices, and these at the most important point in the stroke. This difficulty could not be remedied without taking both engines entirely out-an undertaking for which I had neither time nor means, as the track with which we are now accommodated is soon to be filled up for the purposes of the Railroad company. Another serious difficulty encountered was the breaking of the porous cells in the battery, caus ing a mixture of the two acids, and the interception of a large portion of the power. I had great difficulty in procuring suitable porous cells, and the manufacture of such as I needed was, after a great expense, given up by two of the best pottery establishments in the country as a thing impracticable. It was, however, accomplished through the inge nuity of Mr. Ari Davis, my engineer, but they were made of a weak clay, and have now, from frequent use, become so much impaired as to break from the slightest causes. Before we started two of them broke, and the defect was only partially repaired. Not far from Bladensburg two more gave way, and detracted at once greatly from our working power. On our return, about two miles from Bladensburg, three more gave way, and we were reduced to at least one-half of our power. The running time from Washington to Bladensburg was thirty. nine minutes. We were stopped on the way five times, or we should have probably made the run in less than thirty minutes. Going and coming there were seven stops and three delays-that is, the engine

was backed three times, but without entirely losing headway. It is a very important and interesting feature of this engine, which I demonstrated some years since, that the reversing power is greater than the propelling power; it is nearly twice as great. When the engine is reversed, the magnetic electric induction is in favor of the battery current, and augments its effects. The defect of the cells is easily remedied. The trouble growing out of the oscillating motion of the car can all be obviated by using rotary instead of reciprocating engines. The greatest speed attained on our last trip was about nineteen miles an hour, and about seven more than in any former experiment. CHARLES G. PAGE.

Washington, May 1, 1851.

2. Meeting of the American Association for the Advancement of Science at Cincinnati.-The Cincinnati meeting of the Association commenced on Monday, May 5th, and continued through the week. The attendance was large, and the papers presented numerous and important, as will be seen from the following catalogue. The department which had the most attention was that of Geology, while at the preceding meeting at New Haven there were very few papers on this subject. The papers read are as follows:—

ASTRONOMY, MATHEMATICS, PHYSICS, &c.

On the limit of perceptibility of a direct and reflected sound. By Prof. HENRY, of the Smithsonian Institution.

On an Apparatus for determining Altitudes by means of the Boiling Point. By Prof. J. HENRY.

On the Constitution of Saturn's Ring. By Prof. PEIRCE, of Harvard.

Report of the Committee upon Prof. MITCHEL'S System of Astronomical Observations. By Prof. PEIRCE, Chairman of the Committee.

On a Method of determining the Velocity of Sound by Coincidences. By Prof. A. D. BACHE, Superintendent of the U. S. Coast Survey.

Notes on the Zenith Telescope in determining latitudes in the Coast Survey, by Talcott's Method, and on the reduction of the Observations. By Prof. A. D. BACHE. Current Chart of New York Bay, from Observations in the Coast Survey. By Prof. A. D. BACHE.

Comparison of Curves showing the hourly changes of Magnetic Declination at Philadelphia, Toronto, and Hobartown. By Prof. A. D. BACHE.

On a Modification of Apparatus for the Registration of Time, for Astronomical Purposes by means of Electricity. By W. WURDEMANN, of Washington City.

On the Motion of the Sun about the Centre of Gravity of the Solar System. By Prof. GEO. W. COAKLEY, of St. James.

On a new method of geometrically constructing the Integration by Quadratures. By Rev. TH. HILL.

On the Longitude of the Cincinnati Observatory by Telegraphic Operations, in connection with the U. S. Coast Survey. By Prof. O. M. MITCHEL, Director of the Cincinnati Observatory.

On a new Theory of Statements by Proportions. By Prof. THOMAS RAINEY, of Cincinnati.

On a method of distinguishing between Bi-axial and Uni-axial Crystals when in thin plates, and the results of the examination of several supposed Uni-axial Micas, By WILLIAM P. BLAKE, of New York.

On the Orbital courses of Storms, as opposed to the received hypotheses of general winds, founded on the alleged influence of equatorial temperature. By W. C. REDFIELD, Esq., of New York.

On the Mean Temperature of Cincinnati, and the Methods of calculating Mean Temperatures. By Dr. JOSEPH RAY, of Cincinnati.

On the Effects of the Areas of Oceanic Temperatures on Meteorological Phenomena. By Capt. C. WILKES.

On a new Form of Railroad Curves. By Rev. TH. HILL.

On a curious fact in relation to a Turbine Wheel. By Mr. CHASE, of Mass.

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