Dr. H. J. Johnston-Lavis—The Ponsa Islands. 53 
(8) Brownish red dust bed uae ‘ 0°25 
(9) Pumice bed decomposed at bottom 1-00 
(10) Red ash bed . : ... 0°40 
(11) Pumice bed. The pumice often compact from caleareous infiltration ... 1-10 
(12) Stratified pumiceous dust, red at top : 0°65 
(18) Slightly decomposed pumice bed... ; 0-90 
(14) Finely stratified black dust graduating down into 0-60 
(15) Pumice and lapillo ... 1-80 
(16) Same, but with many fine ash bands ‘and more compact .. 0°60 
(17) Grey pumice and lapillo ... 1-60 
(18) Fine and coarse buff-grey stratified dust, With pumice at bottom. Itis 
compact, pisolitic, and concretionary . 4°80 
iy Brownish earth, with scoria and pumice, a ey irregular bed ... 1-20 
(20) Finely stratified greenish dust bo A ae id 1-60 
(21) Pumice and lapilli, mostly fine 1-00 
(22) Finely stratified buff dust ... aes 1°50 
(23) Pumice and lapillo bed, fine, but more so above ... 1-00 
(24) Stratified buff-grey dust, coarser in stripes with bits of pumice . 1-60 
(25) Pumice-bed, with thin ash bands and finer in upper half 1:13 
1-10 
(26) Concretionary bed of ash... 
(27) Lava and scoria interealated in tufas at south-east angle of the island. 
Maximum height 56 ot apa 
(28) Red earth with pumice and small lava fragments... soc 006 
(29) Band of decomposed pumice, finely bedded 
(80) Fine red earth with concretions 
(81) Pumice-bed with ash bands.. 20: 
(82) Breccia, ash dust, with pumice, banded, probably part 0 of last... 
(33) Pumiece-bed passing up into red dust at top be 000 
(34) Red earthy breccia, stratified with scoria fragments 
(85) Doleritic lavas. 
(36) Stratified lapilli and dust, red at *oP, Beep marine ... So 3°00 
(37) Brown and yellow scoria... 200 cot over 5-00 
Sea-level 
It would be out of place here to go into all the details of each 
separate deposit. I shall therefore simply point out the general 
conclusions to which I have been led from their examination. 
The earliest deposits visible are brown, yellow, and red scoria, 
Japilli, and dust, presenting characters which indicate that they 
were basic essential ejectamenta from a cone in a state of activity, 
not unlike some of the more active phases of Vesuvius. This cone 
seems to have been situated somewhere west of the south end or 
perhaps west-north-west of the island, as this point shows the 
oldest deposits at the highest level, and represents parts of the 
slope of that cone. Also the valleys, if such they may be called, 
radiate from such a theoretical point. 
These deposits were followed by a great and continuous outflow 
of doleritic lavas forming the base of the southern prominence of the 
island. They have been studied microscopically and chemically by 
Doelter. A field study shows them to have been poured out almost 
continually without the intermission of extrusive action, as practically 
no fragmentary materials separate the different streams. In many 
places they show beautifully corded surfaces which would indicate 
their poverty in dissolved water at the time of their issue, the 
phenomena of which must have much resembled the eruption of 
1858 at Vesuvius. The existence of the island depends upon the 
presence of these lavas extending below the surface of the sea, and 
wownwnodre aoe 
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