July 24, 1884] 



NA TURE 



an altitude of 62 miles, and that the air there is a perfect non- 

 conductor of statical electricity, without interfering with the 

 mutual repulsion of similarly electrified particles ; and when we 

 bear in mind that the particles of minute dust are many thou- 

 sands of times smaller and lighter than the gold leaves operated 

 upon, there is every reason to believe that electrified dust, once 

 projected 50 or 60 miles high, might remain there many years. 



Before proceeding further I must draw your attention to the 

 fact that at the time of the great eruption, and during Sep- 

 tember, the mean temperature at Batavia, and throughout Java 

 generally, is at its maximum ; consequently we may conclude 

 that the equatorial belt of calms and uprushing air that encircle 

 the globe was lying over that district at the time. This uprush 

 is caused through the heated atmosphere rising, and the two 

 trade winds, the north-east and south-east, feed it. When this 

 heated air has attained its proper altitude, it flows off to the 

 north and south, but the rotation of the earth causes it to ilow 

 towards the north-east in the Northern Hemisphere, and to the 

 south-east in the Southern Hemisphere, and these winds are called 

 by some the return trades, and by others the south-west and 

 north-west upper currents respectively, and are of great altitude, 

 probably ranging up to 50,000 feet. 



Well, the most bulky masses cast upwards by the eruption of 

 Krakatoa would immediately fall, and the less bulky would fall 

 later according to their size, but the great portion of the dust and 

 ash would be caught, on its downward course, in those upper 

 currents just alluded to, and be carried by them to the north-east 

 and south-east. Such we find to be the fact, for the ship Mtda, 

 when to the westward of Cape North- West, Australia, or about 

 1050 miles south-east of Krakatoa, experienced a fall of dust like 

 fuller's earth, which covered the vessel, on the night of August 

 30-31, and Capt. Tierney, of the brig Hazard, on September 1, 

 near New Ireland, a distance of 3S50 miles due east of Krakatoa, 

 saw the coloured suns, which was no doubt due to the presence 

 of du t in the atmosphere, drifted eastward with the upper 

 current. 



Now, turning to the north-east quarter, or the direction in 

 which the south-west upper current of the Northern Hemisphere 

 proceeds, we find that in Japan during August 29, 30, and 31, the 

 sun was of a copper colour, and had no brightness in it ; at Yoko- 

 hama. Mr. Hamilton states that on the 29th and 30th the sun 

 was of a blood-red colour, and appeared to be obscured. 

 This i, a: a distance of about 3000 miles from Krakatoa, which 

 gives a velocity of the upper current, or return trade wind, of 

 about 62 miles per hour ; this is not excessive, as I have often 

 measured the velocity of the north-west upper current at Adelaide 

 as over 80 miles per hour. 



You may remember that I did not continue the tracking of the 

 dust cloud, from that position assigned to it by Capt. Penhallow, 

 in lat. 24° N., long. 14O5 W., on September 25, because the 

 European and American reports are so peculiar. It was appa- 

 rently seen in England before the rest of Europe, viz. on November 

 4 and 9, in California on the 20th, San Francisco on the 23rd, 

 Italy on the 25th, New York on the 27th. and at Berlin on the 

 28th ; so you see that the geographical arrangement is rather 

 mixed in reference to the order of dates. This may be accounted 

 for by the fact that there was a very severe volcanic eruption in 

 the Alaska Group and Peninsula in October, I think ; it was 

 very intense, and quite capable of ejecting a dust cloud that 

 would envelope the Polar and temperate regions of the Northern 

 Hemisphere ; of course it was not nearly so terrific as that of 

 Krakatoa. So you will see that we must be careful before we 

 assert that the brilliant sunsets of Europe are of Krakatoan 

 origin. 



The phenomena of coloured suns and brilliant sunsets, I may 

 tell you, have been seen before, both in Europe and America, 

 in connection with Vesuvian and Iceland outbursts ; Mr. 

 Somerville, the famous geographer, gives an instance of it which 

 had been seen in Norway, and traced its origin to a severe erup- 

 tion in Iceland. And H. C. Russell, B. A., F.R. A.S., F.R.Met.S., 

 Government Astronomer, Sydney, in his book on the climate of 

 New South Wales, pages 1S7, iSS, gives some most interesting 

 instances of historical accounts of darkened and coloured suns. 

 I will quote them in their chronological order : — 



" ' At certain times the sun appears to be not of his wonted 

 brightness, as it happened to be for a whole year when 

 Caesar was murdered, when it was so darkened that it 

 could not ripen the fruits of the earth.' — Virgil, 

 Georg., lib. i , &c. 



" In 1090 there was a darkening of the sun for three hours. 



' In 1 106, beginning of February, there was obscuration of 

 the sun. 



' In 1208 there was a darkening of the sun for six hours. 



' In 1547, August 24 to 28, the sun was reddish, and so dark 

 that several stars were visible at noonday. 



' In 1706, May 12, about ten o'clock in the morning, it 

 became so dark that bats commenced flying, and persons 

 were obliged to light candles. 



' In 1777, Tune 17, about noon, Messier states that he per- 

 ceived an immense number of black globules pass over 

 the sun's disk. 



' In 17S3 there was a dry fog, and many attributed it to vol- 

 canic action ; and it is well known that in February 

 that year fearful earthquakes in Calabria took place, fol- 

 lowed by a long list of volcanic eruptions in other parts 

 of the world. 



: In 1 S3 1 was an extraordinary dry fog, which excited public 

 attention throughout the world. It appeared on the 



Coast of Africa . 

 At Odessa ... . 

 In South France . 



Paris 



New York ... 

 Canton, China 



August 3 

 9 



15 



end of. 



This fog was so thick that it was possible to observe 

 the sun all day with the naked eye, and without a 

 dark glass, and in some places the sun could not be 

 seen till it was 15 or 20 high. At Algiers, United 

 States, and Canton the sun's disk appeared of an azure 

 blue or of a greenish colour. Where the fog was dense, 

 the smallest print could be read even at midnight. 

 " In 1S73. of the dry fog which came on suddenly in June, it 

 is recorded that it extended from the northern coasts of 

 Africa, over France to Sweden, and over great part of 

 North America, and lasted more than a month. Travel- 

 lers found it on the summit of the Alps. Abundant rains 

 in lime and July and most violent winds did not dissi- 

 pate it ; and in some places it was so dense that the sun 

 could not be seen until it had attained an altitude of 12°, 

 and throughout the daytime it was red, and so dull that it 

 might be looked at with the naked eye. The fog diffused 

 a disagreeable odour, and the humidity ranged from 57 

 to 68, while in ordinary fog it is 100. It had a phos- 

 phorescent appearance, and the light at midnight was 

 compared to that of full moon." 

 Here was exhibited a diagram, drawn correctly to a scale of 

 fifty miles to one inch, showing the arc (15 ) of a circle whose 

 radius was 6 feet 7 inches, or a diameter of 13 feet 2 inches. 

 The Himalayas were shown in their correct proportion, so was 

 the smoke from Cotopaxi, estimated by Whymper while on 

 Chimborazo at 40,000 feet ; he saw at 5.45 a.m. of July 30, 1880, 

 a dense column of smoke shot up straight into the atmosphere 

 with prodigious velocity, which in less than one minute had 

 risen 20,000 feet above the crater, giving the total height of 

 40,000 feet above sea-level. The dust, he goes on to state, 

 fell on Chimborazo after six hours, and he estimated that each 

 particle did not weigh 1/25000 part of a grain, and the finest 

 were still lighter. 



Some, people (and very rightly too) express wonder and un- 

 belief at the possibility of dust being capable of having been shot 

 up to such a height as that ascribed to it, as to cause the red 

 sunsets,— but here' I have quoted the fact of such, as seen by a 

 man of known repute ; the dust and ashes were slut up to that 

 great height, and not only that, but as the dust cloud came 

 between Mr. Whymper and the sun, he saw the phenomenon of 

 the coloured suns. The same may be seen during any very heavy 

 dust storm anywhere, when the cloud is between the observer 

 and the sun. 



In this description given by Whymper, we have a good illus- 

 tration of the tremendous force Nature uses in these convulsions ; 

 a force that could throw the finest dust to a height of 20,000 feet 

 is almost inconceivable to the human mind, and in that pheno- 

 menon we have, I may say, only an everyday occurrence when 

 compared with that giant eruption of Krakatoa. Let us draw a 

 comparison. At the destruction of Pompeii, situated at the 

 foot of Vesuvius, the city was enveloped with darkness from 

 the density of the dust and ash cloud that enshrouded it, and 

 that ultimately buried it ; but now contemplate the tremendous 

 power that ejected from a mountain a sufficiency of dust and ash 



