[10] This monument stands in the centre of the grounds included within the breast-works of the old redoubt on Breed's Hill. Its sides are precisely parallel with those of the redoubt. It is built of Quincy granite, and is two hundred and twenty-one feet in height. The foundation is composed of six courses of stone, and extends twelve feet below the surface of the ground and base of the shaft. The four sides of the foundation extend about fifty feet horizontally. There are in the whole pile ninety courses of stone, six of them below the surface of the ground, and eighty-four above. The foundation is laid in lime mortar; the other parts of the structure in lime mortar mixed with cinders, iron filings, and Springfield hydraulic cement. The base of the obelisk is thirty feet square; at the spring of the apex, fifteen feet. Inside of the shaft is a round, hollow cone, the outside diameter of which, at the bottom, is ten feet, and at the top, six feet. Around this inner shaft winds a spiral flight of stone steps, two hundred and ninety-five in number. In both the cone and shaft are numerous little apertures for the purposes of ventilation and light. The observatory or chamber at the top of the monument is seventeen feet in height and eleven feet in diameter. It has four windows, one on each side, which are provided with iron shutters. The cap-piece of the apex is a single stone, three feet six inches in thickness and four feet square at its base. It weighs two and a half tons.