304 



NA TURE 



{July 24. 1884 



envelop a city in total darkness for thirty-six hours, eighty 

 miles distant. On that diagram I have sketched an imaginary 

 picture of the eruption, and eighty miles distant is represented 

 by a little over an inch and a half, where you see the letter B, 

 showing to your mind the relative distance of Batavia from 

 Krakatoa. You can form in your imagination some idea of the 

 great height that the dust cloud ascended : to my mind twice 

 forty would not be too great. Then again we have the ship 

 Charles /-> r/, when thirty mites distant, was enveloped at noon- 

 day in pitch darkness through the mud-fall. Furthermore, as 

 Lockyer says, the sound, the least part of the affair, was heard 

 over an area of 4000 miles in diameter, viz. in Ceylon to the 

 north-west, at Saigon to the north, and throughout North 

 Australia to the south-east. In the last quarter the reports were 

 at intervals of fifteen minutes, and sounded like ship-guns, but 

 as the hearers were from 150 to 200 miles from the coast, such 

 cause could not be assigned. All that can be said is that it is 

 beyond the human mind to conceive of such gigantic forces, and 

 therefore absurd to throw doubt on the result ; by which I mean 

 that if the laws of refraction show that the substance, whatever 

 it may be, that causes the red glow, is at an altitude of forty or 

 sixty miles, it is ridiculous to doubt that result, when we cannot 

 conceive the magnitude of the power that operated. 



It was not only one eruption that took place, but several, during 

 the 26th, the following night, and up to II. 15 a.m. of the 27th, 

 about which time the grand finale is supposed to have taken 

 place. These eruptions followed each other in rapid succession, 

 and me thought to have been caused by the rapid conversion into 

 steam of vast quantities of water that found admittance into the 

 bowels of the earth. Later on the influx of water was too much, 

 and the result was that a tremendous power was generated, so 

 much so as to cause the north part of the island to be blown 

 away, and fall eight miles to the north, forming what is now 

 called Steers Island. This was followed by a still greater erup- 

 tion, when it is thought that the north-east portion was blown 

 clean away, passing over Long Island, and fell at a distance of 

 seven miles, forming what is now known as Calmeyer Island. 

 These suppositions are almost proved to be facts, from the 

 Marine Survey of the Straits just concluded, from which it will 

 be seen that the bottom surrounding these new islands has not 

 risen, which would most naturally have been the case had they 

 been caused by upheaval, but if anything the bottom shows a 

 slightly increased depth in the direction of the great pit that 

 now occupies the position that the peak of Krakatoa did the 

 day before. These incidents are cited to show you the awful 

 nature and magnitude of the forces brought into play, as you 

 can the more readily satisfy your minds as to the great height 

 the dust and ash were thrown to. 



As I said before, this dust cloud may probably be denser in 

 some places than others, owing that fact to the relative period 

 of time that elapsed between each eruption ; where it is dense we 

 may assume that they followed each other rapidly, and where 

 it is less dense the interval of time was greater. For you must 

 remember that it was shown to you that the cloud apparently 

 moves to the westward, or that the earth moves from beneath 

 tlie cloud, at the rate of S7 miles per hour, so that during each 

 ■ hour of the eruption there was a long streak of smoke and dust 

 being formed. These densest puts were no doubt the cau ol 

 the coloured suns, ami as some observers state, "the sun ap- 

 peared to shine with diminished strength," others "that it was 

 rayless and giving no heat," so we may look upon that dust 

 cloud as playing the part of a great screen, shutting off some of 

 the heat of the sun from us. In these southern latitudes we 

 have experienced those brilliant sunsets for over seven months, 

 and I have no hesitation in expressing my opinion that the re- 

 markably cool and wet summer just passed in New Zealand was 

 due to that dust cloud shutting off the sun's heat in a great 

 degree. And I see from the Adelaide report that the mean 

 temperature there during January was over 4J degrees cooler 

 than the average of the previous twenty-five years, and on only 

 one occasion during that period was it so low, viz. in 1869. At 

 Melbourne also the weather was more like winter than summer, 

 whereas in North and Central Australia, or I may say down to 

 lat. 30 on that continent, the weather was fine, clear, and hot, 

 without rain, giving me the idea that the sun had less power 

 than usual ; consequently the north-west monsoon was very 

 feeble, not penetrating far inland, the result being that the in- 

 terior of Australia has undergone one of the most disastrous 

 droughts on record. But now that, as we may suppose, the 

 equatorial regions of the atmosphere have parted with the 



greater part of their dust, if not all, the sun has regained his 

 usual power, and the north-west monsoon its usual strength, 

 penetrating the heart of Australia with refreshing rains and 

 thunderstorms. So we have here an instance of a most terrific 

 phenomenon that not only brought death and destruction to 

 thousands at the time, but that indirectly caused the death of 

 thousands and thousands of cattle and sheep through drought, 

 and it would be most interesting and instructive to learn 

 whether or not such consequences were experienced in other 

 parts of the Southern Hemisphere at least. 



It would be beyond the province of this paper, and in fact 

 too late to-night, to enter on a history of the tidal and atmo- 

 spheric waves that resulted from this eruption, but I will state 

 two facts to finally clinch your mind of its magnitude. When 

 the earth opened her mouth and swallowed that vast quantity of 

 water, the down-rush that accompanied the closing-in of the 

 surrounding crust was so much as to produce a tidal wave that 

 passed and repassed twice, I believe, round the globe. The 

 other fact is, that the tremendous explosion that accompanied the 

 final eruption produced such a vacuum as to cause atmospheric 

 waves to start, and which traversed and retraversed the earth to 

 the antipodes of Krakatoa no less than four times. 



Some astronomers have thought that the whole phenomenon 

 may be accounted for by supposing the earth to be passing 

 through a dense meteoric track. To my mind, however, the 

 greatest difficulties brought to bear against the volcanic theory 

 are child's play when compared with the possibility of about 

 10,000,000,000 to one of a meteoric track so formed as to have 

 its path, either at aphelion or perihelion, so remarkably coinci- 

 dent with that of the earth as to keep company with her for 

 seven or eight months. Besides, were it either meteoric or 

 cosmic dust, it would be seen all over the earth at the same 

 time, and would be visible all night. 



No ; the only extra-terrestrial argument that would bear any 

 investigation is that of its belonging to the phenomenon of the 

 zodiacal light, which argument, I believe, was adopted at first 

 by my friend Charles Todd of Adelaide ; but, as time goes on 

 and more information is gathered, the volcanic theory, I believe, 

 will be finally adopted. 



THE THEORY OF THE WINTER RAINS OF 



NORTHERN INDIA ' 

 A T first sight, the occurrence of rain in Northern India at the 

 •'*■ season when the north-east or winter monsoon is at its 

 height seems to present a meteorological paradox. The well- 

 known theory of the winter monsoon is that at that season the 

 barometer stands highest in North-Western India where the air 

 is cold and dry, and lowest in the neighbourhood of the equator 

 where it is warm and moist ; and therefore, in accordance with 

 elementary mechanical laws, the wind blows from the former to 

 the latter. But the precipitation of rain requires that the air 

 should have an ascending movement, and this can take place 

 only over a region of low barometer, towards which, therefore, 

 the winds are pouring in. Hitherto no one has attempted the 

 reconciliation of these apparently discrepant conditions. 



Since the establishment ot a Meteorological Department under 

 the Government of India has rendered it possible to study the 

 weather of India as a whole from day to day, it has been my 

 practice to investigate every case of cold weather rainfall in 

 Northern India, amounting generally to three or four in each 

 year, and although many important points still remain for eluci- 

 dation, it is now at least possible to clear up many of the 

 difficulties of the problem, and to reconcile the apparent incon- 

 sistencies. 



The charts which accompany the paper show the distribution 

 of atmospheric pressure and the prevalent winds in the four 

 months of the cold weather. They exhibit many features in 

 common. The region of highest barometer is in the Punjab and 

 the Indus Valley, and from this an axis or ridge of high pressure 

 extends across Rajputana and Central India, having a trough of 

 slightly lower pressure in the Gangetic plain and the Northern 

 Punjab on the one hand, and a much lower pressure in the 

 peninsula on the other. The winter monsoon blows around this 

 region of high pressure in an anticyclonic curve, i.e. in the direc- 

 tion of the "watch-hands, but in the Punjab and the Gangetic 

 plain there is but little movement of the air, the average rate 



1 Abstract of a paper read before the Asiatic Society of Bengal on Mar 

 10S4. by H. F. Blanford, K.R.S., President of the Society. 



