THE STUDY OF COMETS.

Evening Post, Volume LXXIX, Issue 118, 21 May 1910, Page 10

THE STUDY OF COMETS.

* A useful paper has been prepared Toi the Comet Committee of the Astronomical and Astrophysical Society of America for the purpose of informing amateur astronomers and others as to what phenomena may be expected while Halley's comet is *et> visible to us. and how they should be observed. A continuous photographic record, supplemented by as many eye observations as are possible, is, of course, a sine qua non. Good observatories equipped for woik in spectrum analysis are invited to apply visual and photographic analysis to every portion of the comet that is bright enough to give results. Those who possess a refracting telescope of large 'ight-gathering power may do useful polarisation work, especially if they select that part of the comet at which sun and earth subtend a right angle, and compare it with other portions.^ The results may be- of use in determining if part of the luminosity of the comet is due to reflected sunlight, and may throw light upon the size of the luminous particles. Fluctuations of light and their possible relation to the size and orientation of sunspots will also be worth carefully noting. Some idea as to the electrical condition of the comet's tail may be gained by operators of wireless telegraphy. The distance a wireless message can be transmitted will vary with the intensity and distribution of the ionisation of the atmosphere. If, then, when we are passing through tna tail of the comet we iind that the ease or difficulty of sending messages from, say, San Francisco to Honolulu is affected by the ionising action of the tail, useful additions to our knowledge- may accrue. Telegraph anc 5 telephone companies are also requested to report any terrestrial disturbances, as earth-cur-rents of more or less magnitude may be produced with the change in the electrical condition of the atmosphere; but they should also note the occurrence of any other phenomena that may be observed at the same time. Magnetic observatories, especially in the higher latitudes, should carefully watch and report the diurnal variations just before, during, and just- after the passage through the tail, if, warily adds the compiler, such an event takes place. Meteoric trails, the colour of the sun, the existence of a faint reddish-brown coronal solar ring, twilight phenomena, the number of dust particles in the air, the zodiacal light, are also among the subjects selected for observation. The paper in question vvill be found in Science for 11th February.

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