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Show The Eclipse from ait Aeroplane slestt By Gkrrelt P. Serviss. ONE of the mo t interesting astronomical experiments that have been tried in a long time -vvill be Prof. Dpvid Todd's attempt to photograph the total eclipse of the sun to-morrow from a naval aeroplane sent up to an elevation of 10,000 or 15,TH)0 feet from a ship hi the mid-dje mid-dje of the Atlantic Ocean, between be-tween Africa and South America. If it succeeds the . result may be a great advance in our' knowledge knowl-edge of what is, perhap-, Ijje most mysterious phenomenon in the so'.ar system the corona' of the sun which Is believed to serve as an index of the sun's electromagnetic electro-magnetic control over the esrtll. This wonderful phenomenon, which always arouses a profound .sentiment of awe, In every beholder, behold-er, 'appears in the form of a vast "glory," composed of a glowing crown- closely ourrounding the black orb of the uioon ns it covers' the siin, and great rays and stream ers, oiten ot strange shapes, ex-, tending outward from the crown to distances of millions of miles. The corona varies both in general gen-eral shape and in details, as seen during successive eclipses, and thcae variation's are believed to accord in some manner with thu character and Intensity of the solar activity, which are also indicated in-dicated by the existence and mo-. Hons of apparently black spot.-; on the sun's surface. It has been proved that mag-notlc mag-notlc storms on the earth aro somehow connected with these mysterious happenings on the sun. The connection is sometimes startlingly proclaimed by the waving wav-ing in our atmosphere of immense curtains of lambent electric fire, callad the aurora borealis, which is not infrequently accompanied by violent sparks leaping from telegraphic tele-graphic instruments. Unfortunately, owing to the glare produced by sunlight In the atmosphere, the corona cannot he ' seen except when the opaque body of the moon intervenes to. shut ' out, like a black screen, the disk of the sun, whereupon the strange "glory" bursts Into view. Usually the total obscuration by tlyj moon lasts but one or two minutes, but on this occasion It will last more than six mlnutos and a half. ' fr-r BHil JWi ' A total solar eclipse lias rarely -I been seen from a groat altitude because the path of such an I eclipse is narrow and seldom I happens to run over a mountain peak, attainable .by astronomers j with their instruments. For this reasou Professor Todd's observation. If successful, will be unique. At a height of about two m:le3 nearly all the clouds, which often spoil eclipse observations I from lower levels, will be surmo.ir.il-ed, surmo.ir.il-ed, and in addition to that the observer ob-server with his photographic instrument in-strument will be above that part of the atmosphere" which is most ' effective in cutting off the aclinic rays of light which aro the ones that a-T'" the photographic plate. Thu? i reason to hope that j the pi. .jijraphs obtained will be much better, and perhups Incomparably Incom-parably better, than any hitherto takon. ' One great difficulty in the way of astronomical observation presented pre-sented by a ship at sea may be avoided by tho use of- an aeroplane. ! Owing to ttie constant agitation of the ocean's surface, even in calm weather, by the slow heaving and swelling of the surface of the water, wa-ter, it is impossible to maintain t the pointing of au instrument In a 1 fixed direction; but in the the case of a relatively faint phenomenon like the. corona it is necessary to expose the photographic plate for a considerable interval of time in order to obtain a good impression of the light. Of course if the instrument in-strument is swayed by a rocking motion of its base It cannot be kept -steadily pointed at Its object, and only a blurred picture will be obtained. ob-tained. ' With an aeroplane, however, this trouble may be largely, if not entirely eliminated, since the aeroplane aero-plane does not oscillate like a ship, but when held on a steady course glides with remarkable smoothness smooth-ness through the air and moves on ah even beam. If it rolled like a ship it would disconcert the aim, swinging the instrument in-strument through, perhaps, several degrees of arc in a second, but in calm', weather the only motion of the aeroplane is in the direction of Its flight. This motion, as long as. it is straightaway, and its inclination in-clination to the horizontal does not vary, would not affect the pointing of an instrument toward an object at a practically Infinite distance. It would only be necessary to hold the aeroplane on a virtually straight, course during the-time the photographic exposure was being made. On the other hand, If the course were circular the direction of inclination in-clination of the "deck" would swing round all the points of the compass, com-pass, unless tho circling was-per-formcd in a perfectly horizontal plane Efforts to counteract this by means of a gyroscope would probably not prove practicable. 1 Professor Todd has been present at almost every total solar eclipse in the past forty years, and his attempt to see the spectacle this time from the "flies" will be watched watch-ed by the astronomer. of the whole world with deep interest. |