26 St. J ago. paet i. 



and generally bounded by low cliff-formed sides. Por- 

 tions of the basaltic plain are sometimes nearly or quite 

 isolated by them ; of which fact, the place on which 

 the town of Praya stands offers an instance. The great 

 valley west of the town has its bottom filled up to a 

 depth of more than twenty feet by well-rounded pebbles, 

 which in some parts are firmly cemented together by 

 white calcareous matter. There can be no doubt, from 

 the form of these valleys, that they were scooped out by 

 the waves of the sea, during that equable elevation of 

 the land, of which the horizontal calcareous deposit, 

 with its existing species of marine remains, gives evi- 

 dence. Considering how well shells have been preserved 

 in this stratum, it is singular that I could not find even a 

 single small fragment of shell in the conglomerate at 

 the bottom of the valleys. The bed of pebbles in the 

 valley west of the town is intersected by a second valley 

 joining it as a tributary, but even this valley appears 

 much too wide and fiat-bottomed to have been formed 

 by the small quantity of water, which falls only during 

 one short wet season ; for at other times of the year 

 these valleys are absolutely dry. 



Recent conglomerate. — On the shores of Quail 

 Island, I found fragments of brick, bolts of iron, 

 pebbles, and large fragments of basalt, united by a 

 scanty base of impure calcareous matter into a firm 

 conglomerate. To show how exceedingly firm this recent 

 conglomerate is, I may mention, that I endeavoured 

 with a heavy geological hammer to knock out a thick 

 bolt of iron, which was embedded a little above low- 

 water mark, but was quite unable to succeed. 



