520 C. PIAZZI SMYTH ON THE 



most nations appears now to be, that by far the greater part of it must have been 

 supplied by the widely extended volcanic eruptions of 1883, in Australia, in 

 Alaska, but chiefly at Krakatao in the Indian seas. 



Tn each of those three cases, clouds of matter went up, and mud, stones, 

 and coarse dust came down, both speedily and within such immediate 

 proximity of each volcanic vent as to testify unmistakably to their parentage 

 But in the Krakatao case, if not in the others also, a far finer kind of dust 

 went up very much higher ; so high indeed as to be left behind by the earth 

 in its axial rotation ; and thus to be seen successively by every terrestrial 

 meridian in the course of 24 to 35 hours ; and was recognised to be spread- 

 ing out sideways widely and rapidly at the height attained. 



One of these resultant cases, I believe that I saw from the Calton Hill in 

 December 1883 when, after sunset, a brilliantly illuminated display of broad, 

 thin, and nearly uniform cirrus cloud, stretching at one moment apparently 

 through the whole heavens from south, through the zenith to north, — went 

 down with remarkable speed, and in one piece, towards the west, as though it 

 had been a curved shutter of the outer sky, pivoting in the south and north 

 points of the horizon, turning rapidly upon them as an axis, and leaving 

 ordinary clouds hanging about in the lower air, amenable only to petty winds 

 blowing this way and that, near the low-clown surface of the solid earth. 



That any great portion of a volcanic eruption is ever got rid of by being 

 reduced to impalpable powder, projected upwards far above the clouds, and 

 eventually sprinkled in homoeopathic dust-rain over all the surface of the globe, 

 seas and continents alike, and found in rain-gauges — was evidently beyond the 

 ideas of geologists in 1850. For then after a valuable paper read before the 

 Royal Society, Edinburgh, by one of its most respected Fellows, on the volcanic 

 features of the Alban Hills near Rome, — wherein the learned author enlarged 

 on the terrific intensity of the ancient explosions which had blown out the 

 once stupendous rock-contents of their now deep, hollow craters, a gray-headed 

 geologist present inquired with painful care, what had become of that mass of 

 ejected rock? Was it to be found close outside the craters, or at what distance 

 therefrom, and in what sizes and shapes of blocks ? Whereupon the really able 

 author of the jiaper became confused, admitted he had made a mistake, and 

 ought to have said that the supposed blown-out rock-masses had really Mien 

 in ; and that was the reason why they were not to be found lying about in big, 

 recognisable portions outside. 



But with the ultimate Krakatao volcanic ejection which went up, it is said, 

 as a mighty dust cloud, formed of half the mountain's bulk, to a height of forty 

 miles, and under such compelling force as to carry its electrical charge, as due 

 to the interior of the earth with it, and thereby became endued in its every atom 

 with a power of floating perhaps for years above the terrestrial planet, — did 



