On tle 7th of Aug. next a total eclipse of the sun will occur, visible in the United States, at the following points : BEGINNING- AND ENDING OF THE TOTAL PHASE. Begins. Ends, h. m. 8. li. in. s Lincoln, Iowa............................4.29 3 4.32 Des Moins, Iowa.........................4.44 1 4.47 C Iowa City, Iowa..........................4.53 8 4.66 2 Burlington, Iowa.........................4.56 9 4.59 S Keokuk, Iowa............................4.56 3 4.59 c Rock Island, 111..........................4.63 3 5.00 : Peoria, 111...............................5.04 0 5.06 1 Quincy, 111...............................4.57 4 4.59 1 Springfield, 111...........................5.04 8 5.07 c Alton, 111................................5.05 5 5.06 2 Terre Haute, Ind.........................5.15 1 5.17 4 Vincenncs, Ind...........................5.15 9 5.18 6 Louisville, Ky............................5.25 1 6.27 g Frankfort, Ky............................5.28 8 5.81 0 Lexington, Ky...........................5.40 5 5.32 7 Abingdon, Va............................5.42 4 5.44 3 . Wythevil le, Tenn.........................5.45 7 5.47 3 Greeneville,Tenn.........................5.39 5 5.41 3 knoxville, Tenn_____.....................5.36 4 5.39 4 Raleigh, N. C............................5.57 4 5.58 5 WilmiB(rt(m, N. C........................6.01 7 6.04 6 Newborn, N. C...........................6.05 8 6.08 0 The average duration of the total phase will be about two minutes. Some of the prominent central points will be Spring-4ehl and Hock Island, in Illinois ; Terre Haute, in Indiana ; Louisville and Frankfort,in Kentucky; Abington,in Virginia ; and Raleigh and Wilmington, in North Carolina; and Des Moines, Iowa. Coming, as it docs, so to speak, on the heels of the great discoveries of last year, tliis eclipse will attract unusual interest, and be observed with great care. We learn that the Government Las ordered three astronomers, irom the Naval Observatory, to proceed to Des Moines, and two others to Bohring Straits. The Coast Survey, also, will send a detachment of observers to Des Moines, and another to the Missouri River, five hundred mdcs beyond Sioux City. Observations will be made at Burlington, Iowa, by the Superintendent of the Nautical Almanac, and Louisville, ky., will be visited by Prof. Wilson, of Cambridge. Prof. Hough, Director of the Dudley Observatory, at Albany,will,we understand, go to Des Moines ; and Prof. Peters, of Hamilton College will also make his observations at the latter place. lie will be accompanied by prof. William A. Rogers, of Alfred Center, N. Y., and Isaac ii. hall, of New York. The Post informs us that ample preparations have been made by Prof. Peters, at an expense of about twelve hundred dollars, the funds being provided by J\ir. Edwin C. Litchfield, of New York the liberal founder of the Astronomical Department ot Hamilton ColL'ge. It states that the theory of the constitution oi the sun has boon lor years a special object of stu-jy at the Ilaioiilton Observatory, and many special points bearing upon that tlieory will be determined by observations of the coming eclipse. The extreme rarity of this event, also, adds much to its interest, there having boon only two total eclipses, visible in any large part of the United Stales daring the present century : those of 180G and 1834. Annular eclipses are far more frequent, but thour observation is not likely to be so fruitful of discovery as that of total eclipses. We wish the ol)seryers, each and all, a cloudless sky, and success in their arduous undertaking.