52 



Sowerbiensis, yet it is with some reason considered that Ziphius Sower - 

 biensis, the only male specimen that had at the time been discovered, 

 was the male species of that genus, and that the species micropterus 

 was the female ; the difference in the great development of the teeth 

 in the male specimen, and the non-existence or rudimentary state of 

 the teeth in the other, being viewed as sexual. 



The subject of the discovery now recorded was obtained stranded 

 on the shore of Brandon Bay, coast of Kerry, Ireland, on the 9th of 

 March, 1864. 



The skull and jaws, with the teeth, are identical in every respect 

 w T ith the specimen in the Museum at Oxford; it is remarkable as 

 being only the second male specimen known to the European Fauna. 

 The most valuable points in the details given of this discovery are 

 the photographs that were taken of the head of the animal in the 

 recent state, and which have enabled many most important and unre- 

 corded observations to have been made and confirmed, with regard to 

 the peculiar characteristics of the formation of the jaws, and action of 

 the teeth, of this very rare Cetacean. 



Thus, of six of these animals that have been recorded as European, 

 four were females, and two were males ; the two latter having only 

 been met with on the shores of Scotland and Ireland. 



X. — On the Formation of Ground Ice in the Bed of the River 

 Dodder. By Professor Hennessy, F. H. S. 

 [Read April 8, 1867.] 



The formation of ice under flowing water seems to have been long 

 known to boatmen engaged in navigating the rivers of northern and 

 central Europe. At first it was regarded with doubt by many physical 

 inquirers, and its universal recognition as a well-established natural 

 phenomenon has taken place only within a comparatively recent period. 

 Among the properties of water, it would be impossible to name one 

 more remarkable or better known than its loss of density in passing 

 from the liquid to the solid state. The precise determination of the 

 maximum density of water at nearly eight degrees (Fahrenheit) above 

 the freezing point appears still further to interpose a difficulty with 

 regard to the growth of true subaqueous ice ; but, when all the circum- 

 stances under which such ice is stated to have been formed are fully 

 taken into consideration, this difficulty disappears, and ground ice is 

 seen to be the result of general physical laws. 



At the beginning of January in the present year, an instance of the 

 formation of ground ice in the bed of the Dodder* came under my ob- 



* For the information of readers who are not acquainted with the neighbourhood of 

 . Dublin, it may be necessary to state that the Dodder is a stream which rises among the 

 mountains, at a distance, measured in a straight line, of about twelve miles S. S. W. from 

 the city; and that, after sweeping round the south suburban villages for three miles of 

 its course, it falls into the bay, close to the mouth of the Liffey. 



