548 Proceedings of the British Association. 



o'clock at spring tides. This wave is the same which brings to the 

 whole of the Firth of Forth the normal high water, and of the double 

 tides the later of each pair corresponds exactly with the time as predict- 

 ed by the excellent tables of Mr. Lubbock. But if we conceive the 

 great southern wave, which comes up the English Channel, to continue 

 its course northwards in the opposite direction to the normal tide, it 

 would enter the Forth at ten o'clock, being two hours previous to the 

 normal tide, due to the succeeding transit of the moon, or the tide E at 

 Leith will consist of the normal tide due to transit B and the abnormal 

 tide due to transit A. Now the double tides are in exact correspon- 

 dence with these conditions, the abnormal tide being generally about 

 two hours in advance of the normal tide. But the circumstance which 

 most perfectly fixes the identity of the tides, as due to the successive 

 transits A and B, is found in the character of their diurnal irregulari- 

 ties. If the theory adduced be correct, the normal and the abnormal 

 tides will have opposite inequalities. The observations made exactly 

 correspond with this view ; and so far as they go, establish the sound- 

 ness of the view which has been adduced for their explanation. Another 

 remarkable confirmation of this view is derived from the examination 

 of the diurnal inequality of places on opposite coasts at the mouth of 

 the Firth, the diurnal inequality on the south side being that due to 

 the northern or normal tide, and that on the northern coast being that 

 due to the abnormal or southern tide wave. At Leith both waves 

 meet, and the inequalities nearly neutralize each other, and give only 

 the difference of the inequalities. By the same process, using the wave 

 of translation as a type of the tide wave, some further anomalies of the 

 tide wave were explained, and the absence of all tide frequently observ- 

 ed on opposite and adjacent coasts, as at the north of Scotland, and 

 the opposite coast of Norway. These are explained by the fact that 

 the lateral transmission of the wave is slower than its transmission in 

 the direction of its amplitude, so that the rapid advancement of one 

 portion of the wave gives divergence to the branches, which thus sepa- 

 rate and leave an interval of diminished tide or of no tide. 



Mr. Whewell inquired, whether Mr. Russell's explanation of the dou- 

 ble tides supposed the two waves arising from the two tide waves (the 

 northern and southern) to be superimposed ; and remarked, that in this 

 case the difference of successive tides was so small, (only an inch or 

 two) that it required a considerable series of observations to establish 

 its real existence. He remarked, that the difference of the phenomena 

 of tides on different parts of the shore of the same basin is very conspi- 



