SEARCH FOR “ ATILANTIS” 
MICROSCOPE 
HE revival of the idea of a former “ Atlantis” has 
- given rise in recent years to much ingenious 
argument. The presence of so many widely separated 
islands or groups of islets along the depression filled by 
the Atlantic Ocean has to some writers been in itself 
sufficient proof of a submerged continent, the islands 
aining still above water as the last visible relics of 
e foundered land. The same conclusion has been 
awn from the Atlantic soundings, which have undoubt- 
‘edly shown the existence of a long ridge running down 
the length of the Atlantic at an average depth of some 
_2co0 fathoms from the surface. From this ridge rise the 
oceanic islands of Tristan d’Acunha, Ascension, St. Paul, 
the Azores, and Iceland. Other writers have invoked 
the former presence of land over the Atlantic area, from 
the difficulty of otherwise accounting for the resemblance 
‘peck flora in North America and Europe during later 
WITH THE 
geological times. On the other hand, it has been forcibly 
argued that in every case the peaks of the supposed sub- 
merged land are of volcanic origin, that not a single 
fragment of any truly continental rock has been detected 
_on any of these islands, and therefore that no evidence 
“can be adduced save of a submarine ridge on which 
volcanic cones have gradually been built up above the 
sea-level. Reasoning based on similar data furnished 
_by the other great oceans, and also upon the evidence 
‘supplied by the stratified rocks as to the permanence 
of the continental areas, has led many thoughtful geolo- 
_ gists to regard the ocean-basins as primeval depressions 
of the globe’s surface, and consequently to reject the 
tempting hypothesis of a lost Atlantis. 
This vexed question was one on which it was hoped 
that the Challenger Expedition might cast new light. 
The careful surveys of the ocean-floor made by that Ex- 
_pedition, and the attention it paid to the nature of the 
emergent peaks were precisely the kinds of direct obser- 
vation needed to supply facts in place of previous mere 
speculation. We must patiently await the completed 
Reports before the final answer of the Challenger observers 
is given. But an interesting and important instalment of 
evidence and argument has just been published in the 
form of a “ Report on the Petrology of St. Paul’s Rocks,” 
by M. Renard of Brussels, whose name is itself a 
guarantee for the accuracy and exhaustiveness of the 
‘memoir. Sent in to the Challenger authorities as far back 
as October, 1879, it is now issued as Appendix B in 
_ volume ii. of the Warrative of the Expedition. 
No more typically oceanic an island anywhere rises out 
of the deep than the lonely wave-washed rocks of St. 
Paul. Lying nearly on the equator and between 500 and 
600 miles to the east of the South American coast, these 
rocks consist of four principal rugged horse-shoe-shaped 
Masses not a quarter of a mile in their greatest length, 
and mounting into five peaks, the highest of which does 
not exceed 60 feet in height. Their bare rough summits 
have a yellowish tint that deepens into black towards sea- 
level. So utterly barren are they that not a plant of any 
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kind—not even a lowly lichen—clings to their sterile 
surface. Are these rocks the last enduring remnants of 
a continent that has otherwise disappeared, or are they 
portions of a volcanic mass like the other islands of the 
same ocean? 
To those who have not noted the modern progress of 
geological inquiry it may seem incredible that any one 
should propose to solve this problem with the microscope. 
To seek for a supposed lost continent with the help of a 
microscope may seem to be as sane a proceeding as to 
attempt to revive an extinct Ichthyosaurus with a box of 
lucifer matches. Yet in truth the answer to the question 
whether the St. Paul’s rocks are portions of a once more 
extensive land depends upon the ascertained origin of 
the materials of these rocks, and this origin can only be 
properly inferred from the detailed structure of the mate- 
rials, as revealed by the microscope. The importance 
of microscopic examination in geological research, so 
urgently pressed upon the notice of geologists for some 
years past, has sometimes been spoken of disparagingly 
as if the conclusions to which it led were uncertain and 
hardly worth the labour of arriving at them. We occa- 
sionally hear taunts levelled at the “ waistcoat-pocket 
geologists,” who carry home little chips of rock, slice 
them, look at them with their microscopes, and straight- 
way reveal to their admiring friends the true structure 
and history of a whole mountain-range or region. That 
the sarcasm is often well-deserved must be frankly con- 
ceded. Some observers with the microscope have been 
so captivated by their new toy as to persuade themselves 
that with its aid they may dispense with the old-fashioned 
methods of observation in the field. But there could not 
be a more fatal mistake. The fundamental questions of 
geological structure must be determined on the ground. 
The microscope becomes an invaluable help in widening, 
and correcting the insight so obtained; but its verdict is 
sometimes as ambiguous as that of any oracle. In any 
case it must remain the servant not the master of the 
field-geologist. 
Perhaps no more suggestive example could be cited of 
the use of the microscopic study of rocks even in the 
larger questions of geological speculation than that which 
is presented by an examination of the material composing 
the islets of St. Paul. These rocks were described many 
years ago by Mr. Darwin as unlike anything he had ever 
seen elsewhere, and which he could not characterise by 
any name. He found veins, of what he believed to te 
serpentine, running through the whole mass. The ob- 
servers of the Challenger Expedition looked upon the 
St. Paul’s Rocks as composed of serpentine. But these 
remote islets have never until now been subjected to 
modern methods of petrographical investigation. M. 
Renard has studied them chemically and microscopically, 
and finds them to be composed of a granular olivine-rock, 
containing chromite, actinolite, and enstatite. A remark- 
able structure is presented in the thin sections when seen 
under the microscope. The large crystals or grains of 
olivine and enstatite are arranged with their vertical axes 
parallel to the lines of certain bands in which the minuter 
constituents are grouped, the whole aspect of the section 
suggesting at once a movement of the component par- 
ticles in the direction of the bands. When the rock was 
first sliced and examined by the naturalists of the 
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