TRANSACTIONS OF THE SECTIONS. 19 
July, 1843. The following is a short account of the phenomenon as it was observed 
in Arbroath Harbour. 
The neap tides at Arbroath Harbour rise toa height generally varying from eight to 
nine feet. On the 5th of July the moon was twenty-four hours past her first qua- 
drature, and at two o'clock on the afternoon of that day she was in perigee; the neap 
tide on that afternoon would therefore be about its maximum, that is, about nine feet ; 
but at the time of high water at eight o’clock on the evening of the above-mentioned 
day, the tide was at. times observed to rise to a height varying from nine and a half 
to eleven feet; the flux and reflux was first observed about five o’clock in the after- 
noon, and continued up till about the time of high water at eight o’clock. The ver- 
tical depth of each wave was from one and a half to two feet, and the time of flux or 
reflux ten minutes, with an intervening space of from five to ten minutes between the 
rising and falling of each wave. Ihave been unable to ascertain whether the phzno- 
menon commenced or terminated with a rising or falling wave, or to what horizontal 
distance each wave retired or flowed up. The masters of vessels who were a little 
distance out at sea state that they observed a stronger current than usual running at 
the same time that the extraordinary flux and reflux was observed in the harbour. 
The sea at the time (excepting the rising and falling) was perfectly smooth, there 
being then very little wind. Near the time of high water at the two succeeding tides 
the same phenomenon was observed, but not to the same extent as on Wednesday 
evening. At seven o’clock on the same evening a violent thunder-storm came on and 
lasted for the space of two hours, during which the fall of rain amounted to one inch 
and a half, the barometer at 10 p.m. standing at 29-48 inches, and at 10 a.m. next 
morning at 29°42 inches. The Harbour-master at this port, who has observed a 
similar phenomenon before, gives it as his opinion that it is the effect of a storm in, 
the Atlantic ocean, the wind blowing from north-west. 

Remarks on Abnormal Tides. By Mr. Tuomas of Falmouth. 
‘These remarks had been made in consequence of seeing, in a Report of the Asso- 
ciation, the cause which had been assigned by Mr. Russell for the double tides ob- 
served in the Frith of Forth, viz. the interference of the northern and southern tidal 
waves. It appeared tothe writer that this cannot be the rationale of the phenomena, 
since they occur in places where no such cause exists, as in Falmouth; besides, he 
thinks that if this be the cause, it should be observed at Leith, where the meeting 
waves differ two hours in time, and not merely high up in the Frith, He thinks a 
difference in velocity at different parts of its rise, and the influence of strong winds, 
sufficient to account for the phenomena. 

_ On the Nature and Causes of the Diurnal Oscillations of the Barometer. 
By G. Hutcuison. 
__ In the first part of this paper, the author, after stating the leading features of the 
jhzenomenon, argued that the three explanatory suggestions previously advanced re- 
ative to its cause, viz. diurnal variations of temperature, diurnal variations in the 
amount of moisture in the atmosphere, and diurnal variations in the force of the wind, 
whatever influence they might separately and conjointly have in modifying the extent 
of the atmospheric tides and the periods when their maxima and minima are attained, 
were totally inadequate to account for the broad features of the phenomenon, as ex- 
hibited in intertropical climates. The author then ascribed the phenomenon of di- 
urnal atmospheric tides to the ever-varying degrees in which the rotatory and orbital 
movements act, either in union with, or in opposition to each other in different lati- 
tudes during the course of twenty-four hours, and the different seasons of the year. 
_ During night, when the orbital and rotatory movements cooperate more or less in di- 
rection, the excess of acquired velocity through space in the orbital direction above 
the mean of 68,000 miles an hour, must communicate some degree of lateral pressure 
_ tothe atmosphere in the direction of rotation, On the contrary, during day, when. 
__ the orbital and rotatory movements act more or less in opposition to each other, the 
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