66 
GEOLOGY: C. SCHUCHERT 
cable presented great difficulties, and for several days it was necessary to 
drag the grappling irons over the bottom. This was established: The bot- 
tom of the sea in those parts presents the characteristics of a mountainous 
country, with high summits, steep slopes, and deep valleys. The summits 
are rocky, and there are oozes only in the hollows of the valleys. The grap- 
pUng iron, in following this much-disturbed surface, was constantly being 
caught in the rocks by hard points and sharp edges; it came up almost al- 
ways broken or twisted, and the broken pieces recovered bore large coarse 
striae and traces of violent and rapid wear. On several returns, they found 
between the teeth of the grappling iron little mineral spHnters, having the 
appearance of recently broken chips. All these fragments belonged to the 
same class of rocks. The unanimous opinion of the engineers who were pres- 
ent at the dredging was that the chips in question had been detached from 
a bare rock, an actual outcropping, sharp-edged and angular. The region 
whence the chips came was furthermore precisely that where the soundings 
had revealed the highest submarine summits and the almost complete ab- 
sence of oozes. The fragments, thus torn from the rocky outcrops of the 
bottom of the Atlantic, are of a vitreous lava, having the chemical composi- 
tion of the basalts and called tachylyte by the petrographers. We are pre- 
serving some of these precious fragments at the Musee de 'lEcole des Mines 
at Paris. 
The matter was described in 1899 to the Academic des Sciences. Few 
geologists then comprehended its very great import. Such a lava, entirely 
vitreous, comparable to certain basaltic stones of the volcanoes on the Hawaiian 
Islands, could soHdify into this condition only under atmospheric pressure. 
Under several atmospheres, and more especially under 3000 meters of water, 
it might have crystaUized. It would appear to us as formed of confused 
crystals, instead of being composed solely of colloidal matter. The most 
recent studies on this subject leave no doubt, and I will content myseh with 
recalling the observation of M. Lacroix on the lavas of Mount Pelee of Mar- 
tinique: Vitreous, when they congealed in the open air, these lavas became 
filled with crystals as soon as they were cooled under a cover, even not very 
thick, of previously soHdified rocks. The surface which today constitutes 
the bottom of the Atlantic, 900 kilometers (562.5 miles) north of the Azores, 
was therefore covered with lava flows while it was still emerged. Consequent- 
ly, it has been buried, descending 3000 meters; and since the surface of the 
rocks has there preserved its distorted aspect, its rugged roughnesses, the 
sharp edges of the very recent lava flows, it must be that the caving in fol- 
lowed very close upon the emission of the lavas, and that this collapse was 
sudden. Otherwise atmospheric erosion and marine abrasion would have 
leveled the inequalities and planed down the entire surface. Let us continue 
our reasoning. We are here on the line which joins Iceland to the Azores, 
in the midst of the Atlantic volcanic zone, in the midst of the zone of mobihty, 
of instabihty, and present volcanism. It would seem to be a fair conclusion, 
