224 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 16. 



Stood, that this corona was not one and the same in all places, but was different 

 in every differing horizon ; exactly after the same manner as the rainbow, seen 

 in the same cloud, is not the same bow, but different to every several eye. 



Nor is it to be doubted, but the pyramidical figure of these ascending beams 

 is optical : since probably they are parallel-sided, or rather tapering the other 

 way. But by the rules of perspective, their sides ought to converge to a point, 

 as we see in pictures the parallel borders of straight walks, and all other 

 lines parallel to the axis of vision, meet as in a centre. Therefore those 

 rays which rose highest above the earth, and were nearest the eye, seemed to 

 terminate in cusps sufficiently acute, and have been for that reason supposed 

 by the vulgar to represent spears. Others seen from afar, and perhaps not 

 rising so high as the former, would terminate as if cut off with plains parallel 

 to the horizon, like truncated cones or cylinders : these have been taken to 

 look like the battlements and towers on the walls of cities fortified after the 

 ancient manner. While others yet further off, by reason of their great distance, 

 good part of them being intercepted by the interposition of the convexity of 

 the earth, would only show their pointed tops, and because of their shortness 

 have been called swords. 



Next, the motion of these beams furnishes us with a new, and most evident 

 argument, to prove the diurnal rotation of the earth : though that be a matter 

 which, at present, is generally taken by the learned to be past dispute. For 

 those beams which rose up to a point, and did not presently disappear, but 

 continued for some time, had most of them a sensible motion from east to 

 west, contrary to that of the heavens ; the largest and tallest of them, as 

 being nearest, swiftest; and the more remote and shorter, slower. By which 

 means, the one overtaking the other, they would sometimes seem to meet and 

 jostle; and at other times to separate, and fly one another. But this motion 

 was only optical, and occasioned by the eye of the spectator being carried away 

 with the earth into the east; while the exceedingly rare vapour which those 

 beams consisted of, being raised far above the atmosphere, was either wholly 

 left behind, or else followed with but part of its velocity, and therefore could 

 not but seem to recede and move the contrary way. And after the same 

 manner as the stars that go near the zenith, pass over those vertical circles 

 which border on the meridian, much swifter than those stars which are more 

 distant from it; so these luminous rays would seem to recede faster from east 

 to west, as their bases were nearer the eye of the spectator ; and ^ contra, 

 slower as they were further off. 



Nor are we to think it strange, if after so great a quantity of luminous 

 vapour had been carried up into the ether, out of the pores of the earth, the 



