TRANSACTIONS OF THE SECTIONS. 



35 



son, by which a mountain was precipitated into a ravine. On the same day great 

 storms devastated Rhenish Bavaria ; a destructive waterspout fell in the commune of 

 Dembach, and the Garonne and other rivers of France again overflowed. On the 1 2th 

 of May a waterspout fell at Givry, St. Denis ; and another at Beaume on the 15th. 



In Britain the temperature rose 20° F. on the 9th, with the S.W. wind, and con- 

 tinued high until the end of the month. Several accounts from the south and west 

 of France mention the powerful influence of the south and south-west winds at this 

 time in melting the snows on the mountains. 



The barometric curve shows that the centre of the cyclone passed on the 18th, a 

 day signalized by great storms at London, Rouen, and in the South of France. At 

 Nantes on that day, the wind blew violently from the S.W. and then shifted sud- 

 denly to the northward, a well-known indication of the passage of the centre of a 

 cyclone. 



From the 20th to the 30th of May, the faithful barometer registers the passage 

 over Britain of the northern margins of two closely-allied cyclones, whose centres 

 lay far to the southward. In each case the wind veers from S.E. through E. to 

 N.E., and the depressions increase in depth towards the south. 



A very heavy thunder-storm passed over England on the 22nd of May ; at Brad- 

 ford Moor a man was killed by lightning ; the Midland Railway was flooded and 

 several villages inundated. At Leeds the river Aire overflowed, and two lives were 

 lost. 



On the 25th of May two men were killed by lightning during a thunder-storm, at 

 Strabane, in Scotland. 



On the 29th of May, Brighton, Hastings, Portsmouth, and all the South Coast 

 of England, were visited by a violent storm of thunder, lightning, rain, and hail. 



Such were the effects in Britain, which was merely grazed by the northern margins 

 of the two associated cyclones. The effects were much more disastrous in countries 

 farther south, which lay nearer to the centres of the cyclones. Violent storms of 

 wind, hail, and rain traversed France, Austria, Italy, and Spain. The enormous 

 falls of rain deluged the countries already saturated by the previous inundations of the 

 middle of May. At Lyons it rained continuously for forty-six hours, from 7 p.m. of 

 the 29th to 5 p.m. of the 3lst of May. At Ainay, the rain measured in this interval 

 was '30 m. (Iff inches), and at Aux Brotteaux it was '22 m. (8i inches). These 

 rains were general over the western countries of Europe. An indication of the east- 

 erly progress of these cyclones is given by an account of a great storm which broke 

 over Ratisbon on the afternoon of the 31st of May, accompanied by a waterspout. 

 Great damage ensued at Ratisbon. Scarcely one house in Lichtenfels was uninjured, 

 whole roofs were carried away, and the strongest trees uprooted. 



The numerous cyclone-tracks determined by Redfield and Reid all tend to pass to 

 the northward of Great Britain, and this agrees with the well-known predominance 

 of south-westerly and westerh' gales here. But the barometric curves, and the 

 winds, prove that the centres of the twin-cyclones of May 20 to 30 lay far to the south 

 of England. 



Now, as cyclones invariably move, more or less, from the equator towards the 

 pole, their track must have been through latitudes unusually low, at a season of the 

 year when the sun has a high northern declina- May 1856, Bordeaux, 



tion. This passage through an atmosphere of an 

 elevated temperature, and therefore abounding in 

 vapour, will account for the altogether abnormal 

 quantities of rain which they precipitated on southern 

 Europe. 



M. Abria, Dean of the Faculty of Sciences of Bor- 

 deaux, having most obligingly forwarded to me a copy 

 of his Meteorological Observations, taken four times 

 daily, from May 20th to June 6th, I am enabled to 

 determine approximately, as in the annexed sketch, the positions of the centres of 

 the twin-cyclones of the end of May. 



The first cyclone declared its approach at Bordeaux on the 21st by "a very strong" 

 S.E. gale, with thunder and lightning. The centre, therefore, lay to the south of 

 Bordeaux. Where the two cyclones impinge upon and interfere with each other, 



3* 



