290 Dr. Ball—Volcanoes of Barren Island. 
which has been followed may suggest to others, who may not have 
tried it, a graphic means of illustrating geological structure of more 
or less analogous character. 
Notes on toe Fauna. 
Some few remarks on the fauna of these Oceanic islands, as they 
may be called, with special reference to the light thrown by it on 
the question of their antiquity, may, perhaps, be suitably added here, 
especially as the subject has not been alluded to in my previous 
communications. 
While the volcano now called Narcondam is absolutely extinct 
and there is no historical record of its having ever been in a state 
of activity, the volcano forming Barren Island is only in a quiescent 
stage and towards the end of the last century and the beginning of this 
it appears, as has been described on previous pages, to have been in 
such a condition of disturbance that all the animal and vegetable 
life previously existing upon it, was in all probability destroyed. 
The characteristics of the faunas of both islands, so far as they 
are at present known, support these conclusions. The animals found 
on both are immigrants; they consist chiefly of birds and insects. 
Some of them are no doubt voluntary visitors such as the raptorial 
birds, pigeons of strong flight, and aquatic species. There is, how- 
ever, one important species found on Narcondam only, which testifies 
to long continued quiescence on that island. 
It is a hornbill, of which, when we landed on the island in 1873, 
two specimens were obtained and they proved to belong to a species 
previously unknown." 
As there are no hornbills in the Andaman or Nicobar Groups, the 
progenitors of this species must have arrived from some far distant 
region in Indo-China, or possibly in the Malayan Archipelago; and 
their descendants have since developed the specific characters which 
serve to characterize the species. This fact may alone be taken to 
indicate a long period of time, during which the island was, more- 
over, probably not devastated by fire. 
On the cliffs of Narcondam, in quite inaccessible positions, there 
were nests of Collocalia, or rock swiftlets, specimens of which I 
obtained by shooting, and they proved to consist of seaweed agglu- 
tinated by mucilage, and quite different from the true edible nests, 
which were thus proved to be the work of a distinct species. 
As for Mammals and Reptiles there is little to be said; the former 
are represented on Narcondam by a local variety (?) of very dark 
colour, of Pteropus, or Flying Fox, which may have been first 
carried thither by the wind. On both islands rats are found, Mus 
Andamanensis which, possibly, like the few reptiles, namely, 
Hydrosaurus and Skinks, may have arrived on drift timber. 
In general it may be said that the character of the Vertebrate 
fauna indicates its own derivation, through the influence of the 
S.W. Monsoon, from the Andaman Islands, which are about 90 miles 
1 Rhyticiros Narcondami, Hume. 
