a stratum of luminous cloud, floating in a transparent atmosphere. But when we look down through the perforation, we see the edges of other strata, apparently non-luminous. Two of these have been detected, and there may be many more. The sun may then be conceived of as composed of a dark central body, encompassed by successive envelopes or shells, suspended at different heights in the atmosphere—the uppermost being the one which forms the luminous disc of the sun. A Chinese ivory ball, composed of carved concentric shells, represents very well the structure of the sun and the nature of the spots. In looking down the large holes in the ivory ball, we see the successive edges of the concentric shells, and in like manner do we see the successive edges of the concentric strata of the sun. The visible portion of the middle stratum forms the penumbra or shading round the black centre, which is merely the dark body of the sun seen down through the perforation or funnel. But recently another gradation of shade has been discovered, indicating another stratum. The figure at the head of this article illustrates this. The outermost unshaded ring represents the luminous stratum, and the other two interior rings are the non-luminous strata, which may so shade the body of the sun as to fit it for the abode of living beings.
The late solar eclipse was looked forward to with intense interest, as likely to throw new light on the constitution of the sun, and it has not disappointed
