354 Prof. Ehrenberg on the Microscopic Life 
and St. Paul, has recently been examined with the most devoted 
zeal and care, at the special desire of Alexander Von Humboldt, 
by the Austrian circumnavigatory expedition of the frigate 
‘Novara. The great distance of this island from the active 
traffic of the world, and the already published review of the 
larger forms of life accessible to the naked eye, induced me to 
submit the cinders and samples of earth sent to me by Professor 
Hochstetter, the geologist to the expedition, to a careful exami- 
nation in respect of the microscopic forms of life; and I desire 
now to append the results of this investigation, as an expression 
of thanks to the unwearied and most meritorious efforts of that 
observer. 
SHORT DESCRIPTION OF THE ISLAND. 
[From the journals of the ‘ Novara,’ by Dr. Scherzer. ] 
The greatest length of the Island of St. Paul, which, according 
to the recent observations, is situated in 38° 42! 55" S. lat. and 
77° 31' 18" W. long., is three nautical miles ; its greatest breadth, 
from S.E. to N.W., two nautical miles; and its total surface 
1,600,000 square fathoms. Its form is that of a simple crater- 
wall surrounding a nearly circular crater-lake, the latter being 
3984 Viennese feet in greatest breadth, and 34 fathoms (=204 
feet) in depth. The highest point of the crater-margin is 846 
Viennese feet above the level of the sea. 
The rocks are basaltic lavas, consisting of glassy oligoclase 
and augite, with intermixed olivine and magnetic iron. From 
a sharp profile on the eastern side, the petrographic structure of 
the island may be clearly seen. Here four principal periods of 
the geological development of the island make their appearance, 
three submarine and one supramarine, of which more accurate 
proof is desirable. At present the island is only in the state of 
a quiescent fumarole. Pure aqueous vapours, without any trace 
of vapours of sulphurous and muriatic acids, flow forth from the 
clefts of the inner margin of the crater, and, on the summit of 
the island, from the fissures of the newest bed of lava. 
With regard to the period of the last great geological change, 
it appears, from the journals of the ‘ Novara’ of the year 1857, 
that 160 years previously (namely, in 1697, when the Dutch 
captain Willem de Vlaming saw the island) the entrance to the 
crater-basin was still closed by a dam 5 feet in height, and that 
at the present day this entrance is open, for a width of 306 feet, 
for the admission of boats at all times of the day, and has a 
depth of 2-3 feet of water at ebb-tide, and of 9 feet at the flood. 
Whether storms and the action of the waves during the last 
160 years have broken down the dam, or whether au internal 
voleanic movement has assisted in producing the effect, may re- 
