Part 4 of PhD student Geoff Hellman’s in depth study of the eruption of the Laki volcano and the effects it had worldwide. He has kindly allowed us to publish some of his writing.
The dry fog with its attendant storms and other strange and unusual phenomena caused a great deal of disquiet among the more unenlightened of the general population; so much so in fact, that the French astronomer, de la Lande, published a paper in the popular press in which he tried to stifle the rumour and speculation that had been spread by the ignorant.
He accepted that:
“The multitude therefore may be easily supposed to strange conclusions, when they see the sun of a blood colour, shed a melancholy light, and cause a most sultry heat”.
He then goes on to say that there is no need for consternation as this:
“… is nothing more than a very natural effect from a hot sun after a long succession of heavy rain. The first impression of heat has necessarily and suddenly rarefied a superabundance of watery particles with which the earth was deeply impregnated, and given them, as they rose, a dimness and rarefaction not usual to common fogs.”
“This effect, which seems to be very natural, is not so very new; it is at most not above nineteen years since there was a like example, which period too brings the moon in the same position on the same days, and appears to have some influence on the seasons.”
“Among the meteorologic observations of the academy for the month of July 1764 I find the following: “The beginning of this month was wet, and the latter part dry … The mornings were foggy, and the atmosphere in a smoke during the day.” This you perceive bears a great resemblance to the latter end of our June, so that it is not an unheard of or forgotten thing. In 1764, they had afterwards storms and hail, and nothing worse need be feared in 1783.”
Gennari, writing from Padua, gives the impression that other scientists as well as de la Lande, were also trying to calm the fears of the less enlightened:
“The fog was high, dry and dense and this phenomenon was observed not only by us, but also everywhere in Italy, Germany and France, giving the opportunity for some astronomers and meteorologists, by their writings, to dissipate the fears conceived by the lower classes.”
Perhaps the Italian populace should not have been so worried, as the haze due to volcanic aerosols became quite common, there being at least nine confirmed instances of dry fog during the 18th century viz. 1710, 1735, 1775, 1780, 1783, 1785, 1786, 1791, & 1794. In addition, it is highly likely that the population of large cities would have been used to this type of air pollution from the intensive burning of fuel.
Bitter Winters, Spring Floods
There is no doubt that the winter of 1783-1784 coming after the Laki eruption, was one of intense cold, hard frosts, blizzards, heavy rain and strong winds. It was, in fact, one of the most severe winters during the past 500 years. However, we must not forget that the 18th century was still in “The Little Ice Age”, and in hindsight, winters such as this should not appear at all surprising. In fact, the 1783-1784 winter with its heavy frosts, deep snows and frozen soils and rivers was a typical “Little Ice Age” winter, even if more severe.
The onset of sudden rises in temperature was followed by three phases of severe flooding throughout Europe, the latter being the harbinger of a late spring. The dates of these phases are as follows: December 1783 – early January 1784, in England, France, the Low Countries and the Kingdom of Hungary. The second and far more severe phase, began near the end of February and lasted into the second week of March, affecting a much greater area throughout parts of France, the Low Countries and Central Europe. The final phase lasted from late March until the first week in April, and mainly affected the Kingdom of Hungary. The date the thaw started may of course be entirely subjective, depending on the observer, the phenomena observed, his geographical location, the direction of warm winds and rain etc.
The second phase of flooding was one of the most disastrous natural events to occur in Central Europe during the past millennium, and its magnitude may be gauged from the fact that few of the epigraphic markings relating to this event have been exceeded by those of other floods. For example, the flood level of the River Mosel at Cochem far exceeded all previous levels of flooding, whilst the flood marking at Eibelstadt is the highest recorded. However, the mark for the River Elbe in Děčín is well below the flood level of 1845.
That the severity of the winter was remarkable in its intensity was widely covered in the press, as can be seen from the following extracts:
“Flushing Feb. 3. The two Schelds, the Maese, Rhine, Moselle, and indeed all the rivers in these parts, are frozen up. The island of Zealand is surrounded by hills of ice, a circumstance never known before in our memory…”
“Munich (Bavaria), Jan. 19. On the 6th, 7th, and 8th of the present month, Reamur’s thermometer was at 163/4 below the point of congelation (-21°C), three quarters of a degree lower than 1709.”
“At Heidesburgh in the Palatinate, the cold is said to be almost insupportable, and the dread of the inundations on the snow’s melting so alarming, that the inhabitants near the rivers Rhone and Main have packed up their effects, to be in readiness to move on the first signal.”
“…at Rotterdam there is the largest fair on the ice ever known, and with playhouses, and other places of diversion.”
“Hungary, Jan. 20. After deep snow and severe cold, a sudden thaw took place, Dec. 27, 28, 29. Reamur’s thermometer stood for those three days ten degrees below the freezing point (-12.5°C). The Danube and the river of Maros have exceeded their bounds, and occasioned the greatest destruction in their course. The greatest damage was at Newzaz and Arrad; the latter city is entirely under water, and the inhabitants of the greater part of the houses were obliged to go to the tops of them for refuge. . Dec. 30. the misfortune was heightened by a frost, which covered the streets and houses with ice; the frost increased till the 5th of this month, so that the thermometer stood on that day at 23 1-half below the freezing point (-29.37°C). On the 7th of this month it diminished 7 deg.”
“Rome, Feb. 6. Such a vast quantity of snow has fallen during the last week, that the post could not get over the mountains, although 600 workmen were employed in clearing the road.”
“Paris, Jan. 30. Since a month the cold has been very severe in this capital and in its surroundings. There is no single day without snowfall and the frost does not allow one to clear the streets. As there is one foot of snow in Paris, it suggests there are three feet in the countryside and on the roads; everywhere was blocked.”
More next week on The long winter of 1783-1784