There was one aberrant report - from a man named Foley on Cayman Brac, now a small nodule of highly expensive Caribbean real estate, but then a forlorn sliver of a tropical sandspit, a day's sailing south of Cuba. Mr Foley insisted that he heard the banging cannonades, and that they happened in rapid succession on the Sunday. But there is neither corroboration nor a common-sense explanation. There was no eruption anywhere in the Caribbean at the time (it would be another nineteen years before Mount Pelée exploded with classically Plinian intensity); and though freak atmospheric phenomena might be able to explain away this report of the explosion being heard twelve thousand miles away, the fact that Mr Foley also claimed to have heard it twelve hours before Krakatoa exploded suggests his memory, or hearing, was indeed at fault.
Yet there were some oddities about the dissemination of the sounds – not the least being that a great number of people in Batavia, Buitenzorg and west Java generally heard nothing. Others simply felt strangely deaf, or heard a curious buzzing in their ears, or else were aware of wild swings in the pressure all about them, as if they had been caught in some silent atmospheric hypertension. Experts in the field have taken many a stab at explaining why this might be. Some point out that the behaviour of sound waves in the upper and lower atmospheres is very different, and that in the speeding up and slowing down that any wave experiences on passing through them there may be a focus-like phenomenon brought into play that would make one locality receive a lot of sound, another very little. Others, less sophisticated, explain it by reminding us how snowfall muffles sound – and that ash falls, which covered Batavia and its suburbs at the time, are likely to do much the same.
None the less, the overall conclusion remains inescapable, both to historical anecdote and to science: the sound that was generated by the explosion of Krakatoa was enormous, almost certainly the greatest sound ever experienced by man on the face of the earth. No man-made explosion, certainly, can begin to rival the sound of Krakatoa – not even those made at the height of the Cold War's atomic testing years. Those other volcanoes that have exploded catastrophically in the years since decibel-meters were invented – Mount St Helens, Pinatubo, Unzen, Mayon – have not come close: no one suggests that the explosion of Mount St Helens in May 1980 was heard much beyond the very mountain ranges in which it was sited.
Dr Verbeek, with the modest assurance of one who had seen and heard and experienced the vastness of the eruption, stated in his report of 1885 that ‘the exceptionally loud noises require our attention… the large explosions that in loudness have far exceeded all known noises. At no earlier event was a noise heard over such a large part of the earth's surface.’ Under the impact of Krakatoa's explosion, 13 per cent of the earth's surface vibrated audibly, and millions who lived there heard it, and when told what it was were amazed.
The inaudible waves, it was soon discovered, had ventured even further afield. The thousands of Europeans and Americans who noticed and recorded them without in most cases ever realizing just what they were – did so, all around the world, at more or less the same time. The fact that they did so at all points up, quite unexpectedly, one of the newly formed habits of middle-class Victorian society – a set of habits that never anticipated such a catastrophe as Krakatoa, but none the less in due course took full advantage of its effects.
The new-fangled habits of the late nineteenth century included, among the time's multitudes of other scientific advances, the development of increasingly precise means for forecasting the weather. And while cost and complication limited popular access to most other sciences, it did become rapidly possible – and indeed rather popular – for people to buy and use scientific instruments to help them understand the daily fluctuations in their climate. Consequently, as Victorian homes, clubs and hotels filled up their halls and vestibules with the ever newer and more handsome barometers, recording thermometers, sun-gauges and rain-gauges, so the middle classes became an unwitting army of amateur meteorologists, faithfully tapping the glass each day the better to predict whether it would be Fine or Stormy, Changeable or Fair.
The most costly and sophisticated of these instruments was the recording barograph. Because of its price, it was reserved most commonly for the mantelshelf in the club, rather than for the hall at home. The task of this small machine is to record, with an ink trace on a sheet of graph paper secured around the circumference of a clockwork-driven drum, the slight hourly variations in atmospheric pressure over the week that it takes for the drum to rotate a single time.
A well-made barograph is a joy to behold – an elegant confection of brass and steel, mahogany and glass, its mechanicals visible inside its crystal case, its clockwork heart ticking away happily as it takes the pulse of the day. And the ink trace – flowing gently up and down, sometimes more steeply downwards if bad weather is on the way, arching up again if the storm passes over at speed – has a seductively sinuous beauty to it also: the records of the passing week's atmospheric alterations are stored in a small drawer under the instrument, to be studied later, whenever the weather becomes the subject for reminiscence or chatter.
One very noticeable aspect of a barograph's recorded trace is, however, just how smoothly the weather changes. The line invariably curves up or down slowly, steadily. It does not jump erratically, like a seismic record during an earthquake or a lie detector revealing a falsehood. Atmospheric pressure changes with measured deliberation – a feature that the curves on a barograph reflect, with their steady and considered moves across and along the ever unrolling snake of recording paper.
As scores of people around the world came to change their paper for the week that ended on Sunday, 2 September 1883, and as they smoothed the records out to place them away in the drawer, they all, almost simultaneously, noticed something. On the trace for the Monday of the week just gone, the 27th of August, there was a sudden and unanticipated jerk. A hiccup. A notch, an interruption – an altogether most puzzling thing.
The pen that had been so smoothly and seamlessly noting the pressure on the instrument's vacuum chamber had suddenly been flicked up, and then equally violently snapped down again. When looked at more closely, the oscillation was even more peculiar than that: first there was a sudden recorded rise in pressure, then two or three minor oscillations, then a very deep depression, followed by a less steep rise, then more small oscillations, and then finally, after an interruption that lasted for the better part of two hours, back to the smooth and gently changing trace of normal times. In summary, it seemed as though, and for some inexplicable reason, there had been the quite impossible occurrence of an earthquake in the air.
It took only a matter of hours of excited discussion between observatories and weather-fascinated members of the lay public to draw the inescapable conclusion. This, faraway though it may have been, was all Krakatoa's doing.
As soon as news of the extraordinary degree of the eruption had become widely known, it remained a simple matter to check the times of the strange two-hour-long blips on the barograph traces, to make an allowance for the probable approximate-speed-of-sound rate of travel of the shock wave, and to figure in the time difference between Krakatoa and the various club mantelshelves around the world. And lo! they all matched. The eruption that had sent out flame and ash and tidal waves and an incredible explosive sound had also sent an invisible, inaudible shock wave that passed cleanly through the atmosphere, and had been recorded, quite unexpectedly, on scores of machines designed for the much more prosaic task of suggesting to middle-class Victorian gentlemen in Birmingham and Boston and beyond whether they should take their umbrellas to luncheon.
Except that it was, as is much that relates to Krakatoa's eruption, much more complicated than it seemed at first sight. When the traces were examined more closely and compared with other barograph traces from more distant cities around Europe and then around the world, it appeared that the shock wave from Krakatoa's final cataclysmic explosion had travelled around the earth not once but seven times.
All this provoked much fluttering in the scientific dovecotes. Every weather expert in the world suddenly wanted to know what was going on – why a pressure wave like this would behave in this peculiar way. In scientific London the degree of interest was particularly intense – and it prompted what was an entirely unanticipated response: that, despite Krakatoa being on Dutch sovereign territory, it would be best if it were to be left to a distinguished and entirely British body to investigate its eruption.
The high-handedness, seen from today's perspective, quite boggles the mind. Perhaps it was the vast reach of British influence of the day that made this seem desirable to some; perhaps, more specifically, it was the existence of all those records from all those British-owned and British-designed barographs (for all of those instruments, in places as far-flung as Melbourne and Mauritius and Bombay, turned out to have been manufactured in England) that provoked this entirely unwarranted – but it has to be said, quite unresented – example of British imperial busybodyness.
The timetable went like this. The explosion occurred in late August. In early September the British barograph paper records – initially from the leather-bound and entirely masculine fastnesses of London clubland, but later from weather observatories at Greenwich, Kew, Stonyhurst, Glasgow, Aberdeen, Oxford and Falmouth – were changed, and the blips noticed. Suspecting that something of absorbing scientific interest was afoot, a senior British government official named Robert Scott – the secretary to the Meteorological Council – promptly sent telegrams to his colleagues in observatories around Europe, asking if they would examine their traces too.
And back came the reports, from Vienna and Berlin, Leipzig, Magdeburg, Rome, Paris, Brussels, Coimbra, Lisbon, Modena and Palermo and other places besides, confirming in all respects what Scott suspected: that a wave of sudden pressure had swept around and around the planet from its birthplace in the Sunda Strait; that the passage of the wave had been a remarkable event; and that, moreover, it had lasted, echoing around the globe for no fewer than fifteen days following the eruption.
Scott found this quite extraordinary, and told his superior, an old India hand and engineer named General Richard Strachey. In December – only four months after the eruption, and so with unusual dispatch – the pair presented a brief paper to the Royal Society, that most estimable and ancient of British scientific institutions. It was entitled ‘Notes on a Series of Barometrical Disturbances which Passed over Europe between the 27th and 31st of August 1883’. It caused an immediate sensation.
And it did so because here was one of the first provable instances in which a natural event occurring in one corner of the planet had effects that spread over the entire world (or what would be the entire world, if further records could be sought from the Americas and Asia and elsewhere, for they would show the same evidence). Here was the event that presaged all the debates that continue to this day: about global warming, greenhouse gases, acid rain, ecological interdependence. Few in Victorian times had begun to think truly globally – even though exploration was proceeding apace, the previously unknown interiors of continents were being opened for inspection, and the developing telegraph system, allowing people to communicate globally, was having its effects. Krakatoa, however, began to change all that.
The world was now suddenly seen to be much more than an immense collection of unrelated peoples and isolated happenings: it was, rather, an almost infinitely large association of interconnected individuals and perpetually intersecting events. Krakatoa, an event that intersected so much and affected so many, seemed all of a sudden to be an example of this newly recognized phenomenon. And so it was up to a British scientific society – most decidedly a British one, given the imperial mood of the day, like it or not – to investigate it.
A decision to do just this was taken in January, following the reading of two more short papers presented to the Royal Society, both describing the scene on the ground in and around the Sunda Strait. The first paper was by the British consul in Batavia – now a Mr Kennedy from Sumatra, since Consul Cameron had fallen ill – and the other by the socially well-connected Captain Vereker of HMS Magpie, who reported from Borneo. Both papers amply confirmed the view in London that this extraordinary event off Java had been so huge and so world-affecting that a body had to be set up right away to investigate it. And so on 12 February 1884 an advertisement, in the form of a ‘Letter to the Editor’, was placed in The Times:
THE KRAKATOA ERUPTION
Sir – The Council of the Royal Society has appointed a committee for the purpose of collecting the various accounts of the volcanic eruption at Krakatoa, and attendant phenomena, in such form as shall best provide for their preservation and promote their usefulness. The committee invite the communication of authenticated facts respecting the fall of pumice and dust, the position and extent of floating pumice, the date of exceptional quantities of pumice reaching various shores, observations of unusual disturbances of barometric pressure and of sea level, the presence of sulphurous vapours, the distances at which the explosions were heard, and exceptional effects of light and colour in the atmosphere. The committee will be glad to receive also copies of published papers, articles and letters bearing upon the subject. Correspondents are asked to be very particular in giving the date, exact time (stating whether Greenwich or local), and position whence all recorded facts were observed. The greatest practicable precision in all these respects is essential. All communications are to be addressed to –
Your obedient servant,
G. J. Symons, Chairman, Krakatoa Committee *
Royal Society, Burlington House
It took five years for what at first might have seemed a some-what pumice-obsessed Committee to study all of the complex and new types of information that flowed from the event. Their final report, issued in 1888, had 494 pages of text, as well as countless drawings, graphs and exquisite coloured prints. It stood as a lasting masterpiece of determined study, elegantly composed style and splendid Victorian brio – and it collated, among other things, all of the pressure-wave observations that had led to the establishment of the Committee in the first place.
And what was found out about them was simple but remarkably beautiful: that the shock waves from Krakatoa had radiated across the world like ripples on the surface of a pond – the surface of a vast and slightly flattened sphere in the case of the earth, of course, rather than the merely circular surface one would find on a pond. They had radiated outwards at a speed approximating that of audible sound: between 674 and 726 miles per hour.
The waves had travelled outwards, expanding their width until they were halfway to their goal and then contracting again until they reached their precise antipode – which, in the case of Krakatoa at 6°06'S, 105°25'E, is a point (at 6°06'N, 105°25‘W) in the Pacific Ocean off Botoga, Colombia. Then, having taken
The sound of the great explosion could be heard as far off as Rodriguez Island, nearly 3,000 miles from its origin. Records suggest that people living within the shaded area were well able to hear the rumbling and banging, most thinking it the noise of a naval bombardment.
nineteen hours to reach this nameless and watery antipode, they headed offback again and returned to Krakatoa (with the passage noted on all the barographs in between, at a bewildering variety of places that included St Petersburg, Toronto, the Antarctic island of South Georgia and a village that is now a pretty New York suburb called Hastings-on-Hudson).
Every time the wave was noticed, it was found that the time of its passing agreed with the eruption time that had been marked by observers back in the Sunda Strait. The wave's passage above the Greenwich Observatory, for example, was recorded on all the barographs
' registers – with the sharp upward tic of pressure, the minor ruffles on the record, the sudden downward blip, further ripples, the slow upwards rise to the resumption of normal state – at 1.23 p.m. on the Monday. Krakatoa Time was seven hours ahead of London – meaning that at 10.02 a.m., the local time when the volcano exploded, it was 3.02 a.m. in Greenwich. Subtracting that from the time that the Observatory barographs recorded the blip gives a figure for the wave's travel time of ten hours, twenty-one minutes – the precise figure that could be calculated for inaudible shock waves moving across the 7,220 miles of a Great Circle separating London from Krakatoa.
The Greenwich Observatory corroborated the figures for the first pass – and for the six further passes of the shock as it moved back and forth across the capital before it had weakened to the point where it could no longer be detected. And as it did so, two things became even more clear: that the eruption time was exactly right, 10.02 a.m., and that the world now knew a great deal more about the transmission of atmospheric shock waves than ever before. Meteorology in general profited mightily from the findings; and in the mid twentieth century, when large atmospheric explosive tests were conducted during the Cold War, the way in which shock waves were propagated through the atmosphere was well understood also. The Krakatoa Committee had, even if only in these respects, fully justified its existence.
The tsunamis that killed so many on the shores of Java and Sumatra crossed the world as well. It could be seen from the beginning that up close to the volcano the waves were enormous, and killed thousands. That they then became ever smaller in proportion to their distance from Krakatoa was to be expected. But the discovery that they were in fact so deeply powerful, and radiated away from the volcano so aggressively that they could still be detected in the sea as far away as the English Channel, was the cause of general astonishment.
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