32

THE SUN.

plate. Out of many hundreds of drawings we have endeavouredto select some of the most interesting forms ; hut in actual■observation there seems to he no end to their ever-changingvariety.

Such prominences as these are found to be identical withthe beautiful rose-coloured appearances which, as we havealready mentioned, are visible (even to the naked eye) duringa total eclipse of the Sun . A. few observations of themmade at such times are recorded from the beginning of theseventeenth century onwards. But it was not until the year 1851that Airy, then Astronomer Royal, first pointed out that theway in which the Moon ’s body passed over them, graduallyuncovering them on one side of the Sun while it gradually■concealed them on the opposite side, proved undoubtedly thatthey belonged to it, and not to the Moon ; as to which, evenat so recent a date, considerable doubt existed. In fact, untilthe occurrence of the eclipse of that year comparatively littleattention had been paid to them. Since that date, however,they have been most attentively watched in every total eclipsethat has taken place, and it has been found that in someeclipses those seen have been much larger and more abundantthan in others.

Even when they were known to belong to the Sun , it wasimpossible, before the invention of the spectroscope and thediscovery of the best method of its use, to determine their true■composition and character, much less to see and watch themday by day and hour by hour. Nothing, perhaps, can betterillustrate the remarks with which we commenced our firstlecture with regard to the rapidity of recent progress inastronomy, than the contrast of our present knowledge ofthese remarkable formations with that of thirty years ago.

Since their daily observation has been found to be possible ithas been noticed that they are met with in all latitudes of thesolar globe. They are, however, most abundant over two zones,extending from about 10° to about 20° on either side of the Sun ’sequator, where Sun -spots are also most frequent. But instead ofbeing hardly ever met with over the equator, as is the case withthe spots, they are not much less abundant there than at some