112 BRITISH ASSOCIATION POE THE 



Observatory at Paris. In all probability, many years will elapse before a great 

 storm on land is subjected to an examination so rigorous and complete as that 

 undertaken by M. Liais in the present instance. This storm may, therefore, be 

 adopted as the most satisfactory test that we are likely to have foi some time to 

 come of the correctness of the principles of interpretation which I have already 

 applied to barometric fluctuations, in my report on the relation between explosions 

 in coal mines and revolving storms, — principles which flow directly from the nature 

 of cyclones. The cyclonic interpretation in this case would be — First, that the 

 curves indicate the passage of a cyclonic, of which the centre passed to the South- 

 ward of England. This is inferred from the gradual increase of the barometric 

 depression from the Orkneys in the north to Teignmouth in the south, and depends 

 on the fact that the height of the mercurial column decreases continuously from the 

 circumference to the centre of the cyclone. This inference is confirmed by the 

 observation that the wind blew from the eastward at all the stations. Second, that 

 the cyclone was progressing to the eastward. This is derived from observing that, at 

 each station, the wind began at S. E. while the mercury was falling, veered to E. 

 when the mercury was lowest, and then to N. E. as the mercury rose. The charts of 

 M. Liais fully establish the truth of the inferences derived above from the contem- 

 poraneous barometric curves in Britain. They prove that the Balaklava tempest 

 was a cyclone, moving to the eastward, along a central track which passed to the 

 southward of Britain. It is known that during their transit from the Gulf of Mexico 

 to the western coasts of Europe, across the comparatively uniform surface of the 

 ocean, cyclones preserve an approximately circular form. The excellent chartg of 

 M. Liais, at the same time that they exhibit the progress of the storm day by day, 

 from the shores of Britain across the continent of Europe, to the Caucasian moun- 

 tains and the borders of the Caspian Sea, show also the remarkable modifications 

 produced in the normal condition of the cyclone by mountains and other irregular- 

 ities of the surface of the land. Thus, for example, a portion of the cyclone is 

 delayed nearly twenty- four hours in passing the Alps. The consequence of this 

 and similar obstructions is, that what was nearly a circular atmospheric wave while 

 crossing the ocean, takes the form of a much elongated and somewhat distorted 

 ellipse on land, enveloping an elliptical central area of maximum barometric depress- 

 ion which extends, on one chart, from Dantzicin the Baltic to Varna in the Black 

 Sea. Around this central space the wind still blows continuously in the direction 

 peculiar to the cyclones of the northern hemisphere. In the case, therefore, of the 

 Balaklava tempest, whose nature has been determined with much greater exactness 

 than that of any other tempest on land, we have unequivocal testimony that the 

 principles of cyclonology may be safely applied to interpret the fluctuations of the 

 barometer in Great Britain. 



ON ATMOSPHERIC CURRENTS AT LIVERPOOL. 



This was supplementary to Mr. Osier's previous reports, and related to the 

 diurnal laws of the wind when referred to sixteen points of the compass, giving 

 the mean results of above 70,000 observations. It appeared that at Liverpool the 

 various winds have their maximum and minimum velocity at definite and gener- 

 ally different hours. Thus the E.N.E. wind has its maximum about 5 p.m., the E. 

 at 9 p,m., the E.S.E. at midnight, the S.E. at 6 a.m., S.S.E. at 10 a.m., S. at noon, 

 and the corresponding minimuni3 at twelve hours distance from these respectively. 

 The N.N.E. and S.S.W. have each two maximums and minimums in the twenty- 

 four hours. Generally the maximum velocity is about double the minimum. 



