495 
as showing the approach of fine weather; but when this rise was accom- 
panied by northerly and easterly winds, and when the air at the surface 
of the earth was becoming mingled with cooler particles descending from 
above, it is manifest that the increased pressure was due to the increase 
of density of the entire aérial column over the barometer resulting from 
these influences. Thus the change from a high to a low density of 
the air was necessarily accompanied by convection between the warmer 
and cooler strata, as exhibited by the anemoscope. 
Before, as well as during north-easterly storms, we may thus expect 
precipitation of cold air downwards, and ascent of warm air upwards. 
During a gale it becomes difficult to distinguish these phenomena from the 
merely oscillatory movements impressed upon the lower strata of the at- 
mosphere by the influence of terrestrial impediments. When a shallow 
current of water passes over arough bottom, it assumes a ridged surface. 
If we superimpose additional water, the surface of the current will become 
gradually smooth, and it may ultimately present no sensible inequality, 
as on the surface of a deep stream; but we cannot conclude that the 
oscillatory action of the particles near the bottom has been entirely ex- 
tinguished. The influence of the obstacles upon the motion of the 
current will decrease in approaching the surface, and increase in ap- 
proaching the bottom. 
Thus horizontal currents of air, close to the earth’s surface, are 
necessarily disturbed by the presence of trees, buildings, and other obsta- 
cles, and in this manner they may influence the movements of a vertical 
vane precisely in the way that has been observed. During a storm an 
observed diminution of vertical oscillations of the vane will result from 
diminished violence of the wind, just as the gradual lessening of the move- 
ments of the water-barometer seemed to Professor Daniell to foreshadow 
the cessation of a gale. During comparatively calm weather, very ener- 
getic vertical movements of the atmosphere may be safely grouped among 
the most certain symptoms of approaching disturbances on a grander scale. 
Professor Hennessy read a paper ‘“‘ On Anonymous Publications.’ 
The Rev. Samvet Haveutoy, F.R.8., Fellow of Trinity College, 
Dublin, read a paper— 
ON THE TIME OF HIGH WATER IN DUBLIN BAY, ON GOOD FRIDAY, THE 23RD 
APRIL, 1014, THE DAY OF THE BATTLE OF CLONTARF. 
Some time ago I was asked by the Rev. Dr. Todd to calculate for him 
the time of occurrence of high water, on the 23rd April, 1014, the 
day of the battle of Clontarf; as he believed that such calculation would 
throw important light on the accounts that exist of that famous battle. 
The following is a brief account of the calculation and of its result. 
This result confirms in a remarkable manner the ancient account of the 
battle, with which I was unacquainted previous to making known to 
Dr. Todd the solution I had arrived at. I believe that, in consequence 
of the exact information obtained by the Academy in 1851 of the Irish 
