I believe there is but one explanation possible of the origin of these strata, namely, that the great bed of trachyte at the base is an ancient lava bed; that this, perhaps long after it was consolidated, was covered by beds of ashes and scoriae thrown out by a not far distant volcano, and that at last a great convulsion broke through the trachyte bed and hurled the fragments over the country along with dense volumes of dust and ashes. The angular blocks of trachyte imbedded in the stratum Number 5 in section are exactly the same in composition as the great bed below, and in them I think we see the fragments of the rocks that once filled the perpendicular-sided hollow now occupied by the lake. Looking at the vast force required to hollow out the basin of the lake, by blasting out the whole contents into the air--distributing them over the country so that they have not been piled up in a volcanic cone round the vent, but lie in comparatively level beds--I cannot expect that this explanation will be readily received, nor should I myself have advanced it if I could in any other way account for the phenomena. Still, within historical times, there have been volcanic outbursts, not of such magnitude, certainly, as was required to excavate the basin of the lake of Masaya, but still of sufficient extent to show that such an origin is not beyond the limits of possibility. Thus, in the same line of volcanic energy, not far from the boundary line of the States of Nicaragua and San Salvador, there was an eruption of the volcano of Cosaguina, on the 20th of January 1835, when dense volumes of dust and ashes, and fragments of rocks, were hurled up in the air and deposited over the country around. The vast quantity of material thrown out by this explosion may be gathered from the fact that, one hundred and twenty miles away, near the volcano of San Miguel, the dust was so thick that it was quite dark from four o'clock in the evening until nearly noon of the next day; and even at that distance there was deposited a layer of fine ashes four inches deep. The noise of the explosion was heard at the city of Guatemala, four hundred miles to the westward, and at Jamaica, eight hundred miles to the north-east.