Shoivn by Recording Tide-gauges. 139 



at different times, sometimes they occur together ; at one sta- 

 tion the period at high tide is entirely distinct from that at low 

 tide. 



4. Undulations usually occur simultaneously at stations on 

 the Atlantic Ocean (including the Bay of Fundy), but there is 

 apparently no connection between this occurrence at stations 

 on the Atlantic and stations on the Gulf of St. Lawrence. 



5. Barometric records show no similar periodic oscillations, 

 but they do show disturbances at or about the times of marked 

 secondary undulations. 



6. As the head of a bay is approached secondary undulations 

 do not become more marked and frequent, but apparently less. 



7. According to the best available evidence the period at St. 

 John is less the greater the depth to which the tide fills the 

 Bay of Fundy. 



B. Deductions. 



1. The theory of atmospheric billows does not and cannot 

 explain the characteristic local period of secondary undulations. 



2. As an explanation of the origin of secondary undulations 

 the theory of atmospheric billows seems at variance with cer- 

 tain facts of fundamental importance to the theory (see 4 and 

 6 under A, above). 



3. The seiche theory, which is fully established in the case 

 of lakes, has a high inherent probability and is not at variance 

 with any ascertained facts and in certain respects receives 

 strong confirmation (see 2, first part of 3, 4, 6, and 7, under A, 

 above). 



• 4. Even if the "seiche" theory be correct, it still remains 

 to be explained why the oscillations at certain places are usually 

 binodal, at others trinodal, etc., and why in one striking case 

 (Yarmouth) the oscillations are always uninodal at high tide 

 and binodal at low tide. 



5. The whole subject is apparently much more complex than 

 has hitherto been supposed and it may yet be found that no 

 single explanation will apply to all cases. 



Am. Jour. Sci. — Fourth Series, Vol. XII, No. 68. — August. 1901. 

 10 



