394

HISTOEY OF PHYSICAL ASTRONOMY.

the solar atmosphere, the explanation of the various facts relating to thembecomes more consistent and probable.

1 °. That they are solar and not lunar phenomena is evident from theirbeing invisible for some time after the total obscuration, as well as fromtheir appearance as luminous points, and their subsequent gradual increaseof magnitude. All these facts are stated with great precision by M.Mauvais. They are the results which would obviously follow from thecontiguity of the protuberances to the sun at the upper and western partof the limb, and their gradual disclosure by the motion of the moontowards the east. The last-mentioned fact of the protuberances beinggradually brought into view by the motion of the moon over the sun's diskis distinctly asserted by M. Petit as having been very palpable to ob-servation *.

2°. Near the southern limit of the lunar shadow the moon would projectconsiderably beyond the superior part of the sun’s limb, and therefore itmight be expected that the large protuberances seen elsewhere would con-tinue to be almost totally concealed, so as to appear only as luminouspoints. This circumstance would prevent them from attracting morepeculiarly the attention of the observer, who might consequently be led todiscover similar points of equal minuteness, which might otherwise haveescaped his notice. The truth of this remark will be more apparent tothe reader when he takes into consideration the extreme shortness of theinterval of total obscuration, even at those places that were situate in thevery centre of the shadow, and the variety of circumstances which call forthe vigilant attention of the observer during the lapse of that interval.The phenomena observed at Toulon , which was situate only a short dis-tance within the south boundary of the shadow, is quite consistent with theabove conclusion.

3°. Towards the northern limit of the shadow', where the moon pro-jected only in a small degree over the superior part of the sun’s limb, itmight be expected that the protuberances would become visible imme-diately after the commencement of the total obscuration. This circum-stance actually occurred at Yisan, as has been already mentioned. It isdifficult, however, to account for the smallness of the angular dimensionsunder which the protuberances appeared at that place. Perhaps it arosefrom the shortness of the interval of total obscuration, not allowing theeye sufficient time to recover from the dazzling effect of the sun’s light,so as to take due advantage of the obscurity which actually prevails. Wehave seen that the nonvisibility of the stars of the second magnitude duringthe total obscuration has been referred with great probability to the samecause.

Admitting, then, that the phenomena had an intimate connexion withthe sun, there are various facts which render the supposition of theirmeteorological origin extremely probable.

1°. The reddish colour of the light emitted by them indicates that theypossess the property of absorbing in a great degree all the rays of the

* It is not to be denied that the size which the protuberances ultimately acquired, whentaken into consideration with the fact of their first appearance after the total obscuration,as mere luminous points, considerably exceeds that which this explanation of their appa-rent growth would assign to them. It is to be remarked, however, that when they firstbecame visible, the eye had not in all probability recovered from the dazzling effect of thesun’s rays, so as to discern fully the portion of each protuberance that was already disclosedto view.