BLACK ASH.
The city and environs of Honolulu are widely covered by a coarse black ash, cinders or sand of volcanic origin. It is so coarse and uniform that it has been utilized for the removal of all sorts of sewage from the houses to the sea. When the population was sparse this material rendered the laying of cement pipes un necessary, as it removed the waste matter in a satisfactory man ner. Now that the population has greatly increased, there is a call for an improvement over this primitive method of drainage. Nevertheless, facts about the distribution of this ash will still be of importance, as it will be years before all parts of the city can be reached by the new sewers.
The extreme northeastern limit of the black ash is at the base of the Tantalus cone, where it is well exposed along the road for a quarter of a mile. As much as twenty-five feet thickness of it is presented to view here. Some of it is weathered, and there are numerous small nodules scattered through it, varying in size from grains to a length of two inches. Some parts seem to be consoli dated lumps, both black and red.
The spur running down to Kakea and Roundtop toward Ma kiki is covered by this sand, to the obscuration of the underying rock, nearly all the way from Tantalus. A small pond east of Kakea, seemingly an old crater, is sometimes spoken of as the source of the great flood of ash, as it is continuous from it over the top of Kakea, 1,460 feet high, and all the neighboring sum mits. All these hills have rounded slopes, as if they had been de luged by showers of sand. It poured down the Manoa slope as far as to the trolley line. Roundtop, 1,062 feet, is overlaid by the same material, and everything is covered down to Wilder avenue and beyond. The road from Punahou tip to Manoa Val ley and the north side of Rocky Hill shows it nearly everywhere. From Oahu College along the base of the hills sloping down from Tantalus and round the base of Punchbowl the amount of this ash reaches its maximum thickness.
Much may be learned by studying the phenomena presented ahout Punchbowl. First, however, it must be stated that this material is used much for grading and filling holes in the ro-ads, and about buildings. Soon after its application it becomes rusty, and in a year or two the color has completely changed, so that it is not recognizable. The reddish color of the road and the
sidewalks all over the city indicates its presence to those who understand what the black ash may become, and its pulverization gives rise to the dust so freely blown by the trade winds into one's face all over the city. A very prolific source of it is from the slopes of Punchbowl, where it may be seen in abundance, both in the original and altered conditions. At the "Battery," on the summit of the road, this ash occurs in connection with scoria, lapilli, and basalt. It is apparently the throat through which there have been copious discharges. The greater part of the in side of the bowl is covered by it, and those who believe the whole material came from Tantalus would say it had rained down into the bowl from the sky. Nearly opposite the lowest point in the rim of the bowl there is a hill (one hundred and ninety-seven feet) known as the "Powder Magazine," entirely composed of this sand, said by some to have been blown out there from Punchbowl. While this may be true, it is not necessarily so because of excava tions of the ravine between the Magazine and the Bowl by run ning water.
The most westerly exposure of these ashes is at an old cemetery between the Insane Asylum and the Bishop Museum. Obviously the Nuuanu valley may have been filled with this deposit, which has nearly all been removed by fluviatile erosion, leaving this remnant of one or two acres in extent. This may be ten feet thick, as shown by excavations, with caves and pillars of a similar material made to cohere by concretionary attraction. Here may be seen the pebbles overlying the ashes. They have been seen also on the north side of Punchbowl. Hence there are three localities of stones thrown out from Punchbowl subsequently to the discharge of the ashes. It is to be noted that the ashes at the crest of Punchbowl near the flagstaff and those below Tan talus and over Roundtop contain numerous nodules. These are not present in the deposit in the lower grounds about the city. Perhaps their greater weight explains why they are limited to locations near their point of departure.