478 PHILOSOPHICAL TBANSACTIONS. [aNNO 1720. 



a very vivid red, which was instantly and gradually succeeded by the other pris- 

 matic colours, all vanishing in about a second of time. These colours affected 

 the sense so strongly, that I thought them to be more intense than those of the 

 brightest rainbow I had ever seen. A small time before the appearance lost its 

 perfection, we were surprised to observe a shaking and trembling of the streams, 

 chiefly in their upper parts, during which their convergence was confounded, 

 and the whole heaven seemed to be in a convulsion. At the same time I could 

 perceive waves of light towards the north, which moved upwards, and in their 

 motion crossed the streams, lying parallel to the horizon. Their breadth seemed 

 to be about a degree, their length about QO degrees, and I can compare them 

 to nothing better than to those slender waves on the surface of stagnant water 

 made by throwing in a small stone. 



About 7 or 8 years since, I saw another meteor. Along the horizon in the 

 north, there lay a white and luminous, and seemingly a dense matter, in the 

 form of a cloud, represented by abed, fig. 1, pi. 13, its length, a b, was about 

 10 or 15 degrees. From this there arose, directly upwards, pointed streams of 

 the like luminous and white matter, which yet did not appear in any part of it 

 to be so dense as the former, and which became gradually more and more rare 

 in its upper parts, so as to vanish almost insensibly at the points. There was 

 some little difference in the height of these streams, but they generally ascended 

 up to about 4 degrees above the horizon. They were very numerous, and con- 

 tiguous to each other, and seemed to be composed of very slender parallel fila- 

 ments or rays. Sometimes a fire or flame would break out in the cloud, abed, 

 and move along it in a direction parallel to the horizon ; and during this motion 

 a pointed stream directly over the fire seemed to run along with it, and to pass 

 by the other more fixed streams, to which it always kept itself parallel. 



I am persuaded that the late appearance was of the same kind with this. For 

 let AB, fig. 2, represent the plane of the horizon, c the place of the spectator, 

 EF, a fund of vapours or exhalations at a considerable height, diffused every way 

 into a large and spacious plane, parallel to the horizon. This fund of mixed 

 matter by fermentation will emit streams from itself, such as eg, ph, &c. which, 

 if the wind be perfectly still, will ascend perpendicularly upwards; if it be bois- 

 terous and irregular, they will be blended and confounded together; but if it 

 be very gentle and uniform, as it was at the time of this appearance, they will 

 be inclined towards the point of the horizon, which is opposite to that from 

 which the wind blows. Now if adb represent the concave of the heavens, 

 and a line, CD, be drawn parallel to the columns eg, fg, &c. it is certain, by the 

 rules of perspective, that these columns will appear on that concave to converge 

 all around towards the point d; thus the column eg will seem to arise from the 



