REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.


and the vegetable imprints of the schists, -are above the limestone and produce (km. 49) a true lignitic stratum. A similar stratum, perhaps the same, reappears near the ridge between kilometers 54.50 and 55.50. It contains here melanites (?) and a small congeries, but the fossiliferous limestones of kilometer 49 are faulted. Mr. Cayeux found only one foraminiferous specimen in the strata below the lignitic layer.
 These facts can be summarized as follows:
 On the Pacific slope the Gamboa rock supports a formation which occupies the place of the Vamos-Vamos strata, but has only the richness in volcanic elements in common with them. This formation, composed of bituminous schists and grit, has a more coast-like appearance, accentuated by the abundance of terrestrial plants, and is even partly marine, as is shown by the presence of a congerie. It grows in thickness as it recedes from the anticlinal central arch, and is overlaid by Miocene limestone, where another lignitic layer is interjected.
 Therefore, from what precedes, there are no sufficient reasons to classify the Culebra system under the Aquitanian. This might be a local stratum of the lower Miocene; but the outcroppings of the calcareous strata, worked in former times to provide limestone for kilns near the station of Emperador, render this last assumption improbable.
 These calcareous layers were examined by Mr. Hill. He describes them as situated at about 3 kilometers (1.86 mi.) from the northwest side of the top of the Culebra, near Emperador station, and forming two small outeroppings near a ravine among the superficial red clays. At the distance of about 20 meters (65.61 ft.) farther down appears the volcanic rock, and 100 meters (328 ft.) to the north, in the railroad cut, we find stratified clay of the Culebra system.
 Mr. Bagg, who examined a cut of this limestone, has found nummulites, an orbitoide, and other Foraminifera (Cristellaria, Rotalia, Nodosaria). The nummulites are the predominating types. This association of the nummulites and orbitoYdes reminds us of the Bohio rock, and it is very probable that we have here an Aquitanian limestone; at all events it is not Miocene. Mr. Hill says that we can not see the stratigraphic relation of the calcareous material with the neighboring formations, but it is his impression that it is a lenticular bank of limestone, included in the Culebra system. This opinion is confirmed by the results of the Richier boring (km. 53) of the old company. This boring, situated immediately opposite, at about 500 meters (1,640 ft.) from the preceding outcrop, shows a very hard, compact layer of limestone only 5 meters (16.40 ft.) thick, intercalated between bituminous schists and grits which are not shown by the adjacent borings. It is presumably the same limestone, whose position would thus be determined without ambiguity and would establish the Aquitanian age of the entire Culebra system.
 It must be remarked that there is, moreover, a calcareous outcrop in the railroad cut at the station of Emperador and another at Las Cascadas (note of Canelle). But this limestone is quite different; it is lumachel with Ostrea' and Pecten, containing with polypiers the Pecten sbplenronectes, identical with the limestone of kilometer 49, which is doubtless connected by a series of continuous outcroppings. We shall later consider the proofs of the Miocene age of this limestone when we shall speak of the mollasse "(Fr.) of Alhajuela.
 It remains to mention in the system of the Culebra the intercalation of tuffs and contemporaneous andesitic flows. One of these flows has been followed by the drift gallery at level 41; similar rocks have been found in several shafts at levels which do not permit us to consider them as one flow. The microscopic examination shows besides, independently of the presence of tuffs, that it can not he an intruding layer.
 Paciic slope.-Beyond the large cut the lignitic system sinks and disappears below the sea level. The knowledge of this part comes only from the old canal work and the numerous intrusions of volcanic rocks, perhaps accompanied by faults which render their interpretation considerably obscure. However, two important facts are clearly shown: First, the reappearance of the limestone of kilometer 49 with the same fossils at kilometer 59.40 at the projected location of the lock of Pedro Miguel. This limestone seems to be intercalated in the upper part of the lignitic grit, and contains oyster shells, the Pecten subpleuronectes, and rounded orbitoYdes. The borings permit us to follow it up as far as kilometer 60.30; they show it again at kilometers


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