AAQ NEW ZEALAND. 
Throughout this region, we have instructive examples of the pro- 
tection afforded by the sea against decomposition. ‘T'ie whole coast 
of the Bay, and of nearly all its islands where the rocks are not 
interrupted by a beach, is bounded by a rocky platform twenty to 
eighty feet wide. This platform is very regular in height, lying near 
the level of two-thirds flood tide, that is, between five and six feet 
above low water, the tide being eight feet in this region. The exist- 
ence of this platform is owing to this protection of the sea from wear 
and decomposition. Above, the material has disintegrated and been 
washed away by the action of streamlets and the waves; but beneath 
the water, these effects do not take place. The cause for the particular 
height of the platform has already been explained (p. 109); and we have 
alluded to the singular forms of some of the islets. We repeat here 
the figure of “The Old Hat,” with its broad brim. As the rock is not 
stratified, the sea does not, under any circumstances, tear off and 
throw up large masses on the shores. ‘The surface of the platform is 
generally covered with a muddy coat, a fourth of an inch thick, which 
is very slippery under foot, owing to its clayey nature. This coat is 
the softened exterior of the rock. Notwithstanding its softness, it is 
too adhesive to be easily washed away by the surf. 
The soil which covers the country for several miles around the Bay 
of Islands, has arisen entirely from the rocks beneath. 
Igneous Rocks and Volcanic Phenomena. 
In the vicinity of the Bay of Islands, there are basaltic rocks, and 
several extinct craters. 
Several low tabular islets occur off Tipuna, in the Bay of Islands, 
which consist of a dark compact basalt. ‘They constitute a cluster by 
themselves, unlike the rocks of either shore, and stand with abrupt 
sides, and an even height of about thirty feet. The low cliff which 
forms their outline shows a columnar structure, in some places quite 
perfect and regular. The rock is very solid in texture, scarcely 
glistening on a surface of fracture, and contains disseminated crystals 
