68 



or axis of vibration will describe the surface of two coues having 

 their common apex in the axis of rotation. 



The axis of a flexible pendulum can only assume a position ver- 

 tical to the point of the earth's surface over which it is placed. 

 Were it possible to maintain the vibration of a stretched wire occa- 

 sioned by an original impulse, for a sufficient length of time, the 

 apparent rotation of its plane of vibration would vary with the in- 

 clination of the wire to the axis of the earth : placed in this axis, it 

 would make a rotation in 24- hours, it would become progressively 

 slower according to the law above given, as it approaches the plane 

 of the equator, and when anywhere in this plane the vibrations 

 would always be performed in the same direction. 



2. " Report of further Observations made upon the Tidal Streams 

 of the English Channel and German Ocean, under the authority 

 of the Admiralty, in 1849 and 1850." By Captain F. W. Beechey, 

 R.N. Communicated by G. B. Airy, Esq., F.R.S. &c., Astronomer 

 Royal. Received March 27, 1851. 



This is the continuation of a report which the author made upon 

 the tidal phenomena of the Irish Sea and English Channel in 1848. 

 After detailing the manner in which the investigation had been con- 

 ducted, and the great care w hich had been bestowed upon the ob- 

 servations, which are numerous, the author enters into an explana- 

 tion of the w^hole system of tidal streams in the English Channel and 

 North Sea, as deduced from these observations, and also as to what 

 he considers to be the cause of the peculiar movement of the streams 

 in these channels. Ele supposes, in conformity with Dr. Whewell s 

 theory, a tide-wave to pass along the western shores of Europe, and 

 to enter the English Channel and North Sea by opposite routes, and 

 to arrive off the Texel and Lynn at the same tidal hour as the tide- 

 wave in the English Channel arrives off the Start and Jersey. 

 From these points there are thrown off branch or derivative waves, 

 which differ materially both in dimensions and rate of travelling from 

 the parent wave. These waves roll on towards the strait of Dover 

 and there merge into each other and form a combined wave. 



The effect of this Vt^ave upon the tidal establishments of the Chan- 

 nel had long been known ; but its influence upon the streams of the 

 Channel had never before been considered, nor had any observations 

 upon them been systematically undertaken. 



In arranging the plan of observation the author considered that, 

 as the combined wave was common to both the English Channel 

 and North Sea, the tidal streams of both these channels would be 

 found to correspond in every important particular, and that the 

 movement of the streams throughout the strait would be materially- 

 influenced, if not wholly governed, by the motion of the combined 

 wave ; that the time of this wave attaining its greatest altitude would 

 thus afford a standard to which the turn of the streams throughout 

 the Channel might be advantageously referred ; and that there would 

 be found in this Channel, as in the Irish Sea, which is equally under 

 the influence of a combined wave, a stream which would turn nearly 



