REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.


This inclination creates, from the point of view of the stability of the layer of red clay on the left bank, unfavorableconditions that have already caused the sliding at Cucaracha. This sliding has long since stopped and the engineers do not fear its recurrence. We must, however, repeat that it will be prudent to rather exaggerate the preventive measures.
 As an example of the composition of the sandstone formations, we cite the diagnosis from kilometer 53.534:
 Sandstone, nearly half of which is composed of quartz; aggregations of quartz are frequent; there are fragments of very much altered eruptive rocks, more or less greenish; some pieces of andesite and isolated feldspars; green grains with rounded contours which might be glauconic; the cement is composed of an argillaceous matter.
 Comparing it with diagnosis from kilometer 54.20:
 Fine level sandstone; grains somewhat mixed with quartz; angular debris of feldspar and augite; grains of limonite and chlorite slightly rounded. Argillaceous and ferruginous cement, containing undeterminable crystals; some lapilli of volcanic rocks, much altered and scarcely recognizable.
 As an example of the schist formations we also cite a few diagnoses:
 Kilometer 54.680.-Gray coherent clay. Under the microscope is seen a sedimentary clay, partly crystalline, containing small pieces of quartz and pieces of altered feldspar.
 Kilometer 55.465.-Greenish-gray rock studded with green grains. It is a very crystalline clay, containing numerous glauconic grains, of which one includes several organic debris, among which one is foraminiferous. Clastic quartz very rare; pieces of altered feldspars; a few fragments of glass and of a microlitic much-altered rock.
 Kilometer 55.645.-Maroon-gray rock having the appearance of a desiccated clay. It is a very fine clay, composed of an intimate mixture of amorphous matter and fine crystalline particles. Small veins and streaks of a dirty yellow, fibrous, doubly refracting matter. Occasionally small grains of elastic quatz.
 Kilometer 55.513, level 41.-Clay. Lapilli of small pebbles of basic rock, much altered, cemented with a ferruginous clay, which itself seems to come from the decomposition of similar materials; occasional grains of quartz.
 Finally a white clay, found on top of the lignitic layer at the base of the altered series, gave to Mr. Cayeux the following composition:
 White clay, very coherent.--Under the microscope is shown an extremely fine clay, the greater part amorphous, with streaks and small particles of well-rounded calcite. There are a few pieces of elastic quartz.
 We must observe that all of the preceding diagnoses apply to specimens from the upper part of the cut, obtained near flows of volcanic rocks. From a lot recently forwarded we have been able to examine pieces of bituminous schists coming from deeper levels cut by the test borings. The proportion of volcanic fragments is much smaller and the bituminous matter seems, under the microscope, to assume the form of black patches. Foraminif era are abundant in these cores. Mr. Cayeux, as we have said, has recognized sections of textularias and globigerinm.
 Toward the upper part of the cut we find an intercalated layer of eruptive rock, which from the points determined in different places appeared to us slightly oblique to the strata, and which we at first attributed to an intruding layer. It is not so; it is a flow accompanied everywhere by incontestable tuffs. The obliquity of its bed is without doubt due to the fact that there are several flows of slightly different levels. We give here the diagnosis of the rock-(km. 34.30, level 70):
 Gray andesite.-Crystals of labradorite slightly zoned, containing about 65 to 70 per cent anorthite. "Pite fluidale (Fr.) to a great part still vitreous, but which must have been originally entirely vitreous, and which has been partially devitrified.'' The product of this devitrification seems to be a feldspar probably more acid than that of the large crystals.
 A few crystals of apatite; a few grains of Fe304. The absence of magnesian minerals seems complete. This specimen seems to come from a true flow. The rock is, considering the region, of remarkable acidity. None of the other 31 specimens examined show any resemblance to it. The veined rock obtained at a point very near the former is entirely different.
 With regard to the tuffs which accompany this flow there are several diagnoses which are not of doubtful character:
 Kilometer 54.40, level 72.-Tuff or cinerite. Lapilli of various eruptive rocks, considerably decomposed; vitreous debris; numerous debris of crystals, feldspar, and augite; clayey cement.
 Kilometer 54.58.-Grayish-green rock showing some pieces of vitreous feldspar. Under the microscope we see numerous debris of microlitic rocks with an entirely crystalline or noncrystalline mass; we find several pieces of andesite. The feldspars of these andesites are more often small microlites and occasionally elements of large size, which make of the rock a kind of diabase. There are large isolated pieces of basic feldspar, generally fragmentary;


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