HORIZONTAL PASSAGE TO QUEEN'S CHAMBER. ON March 3d the level of the floor of this passage (for the part extending from the north end towards the south, but only to the edge of the deep step, or 1303 inches in length), was tested with the sextant-horizon by means of reciprocal angles, with the result of finding a dip southward = 0° 7′. On March 10th, the level was again tested, and by the circular clinometer on its long 126-inch foot; but as the floor is very rough and uneven,-no proper passage flooring at all,-it could only be brought to bear between the distances 200 and 1300, from the north end of the Grand Gallery: the results, corrected for index-error = 24', were as follows: The two instruments seem tolerably confirmatory of each other; but when I tested afterwards the whole length of the passage, by looking along its ceiling from the Queen's chamber, to a scale set up by the north wall of the Grand Gallery, there was a dip northwards indicated, amounting to several inches, and equivalent to not less than 0° 8'. It is possible, however, that part of this apparent quantity, is owing to the ceiling bending down somewhat in the middle of its length. GRAND GALLERY ANGLE. SEXTANT-HORIZON. March 3.-This instrument was placed on a stand previously prepared to suit the spot, and to stand partly on the sloping floor of top of first ascending passage, and partly on flat floor leading to Queen's chamber; the instrument was then nearly in the plane of the doorway, or north wall of the Grand Gallery; and its position as to height, was 28.5 inches above floor, and 24.5 below ceiling, of first ascending passage, or two inches vertically too high. At the other or south end of Grand Gallery the signal was a candle shining through a 1.1-inch hole in a board; first naked and afterwards through oiled paper. The board was held by hand in plane of south wall, or in south doorway of Grand Gallery; and the board was cut to such a length that when resting on the floor there, the hole was 18 inches above the ground,-equivalent to 25.0 inches above the line of the Gallery floor, continued up to the south wall, or through the substance of the 'great step;' and 250 inches below roof of short horizontal passage leading to antechamber: it was therefore in the concluded axis of that passage. Above the first hole, by 3.5 inches, was a smaller one of 0.6 inch diameter, similarly illuminated. The mean of the two holes was therefore 1.75 inch too high; or 0.25 lower than it should have been, to be similar to the error of the instrument at the other end. The observations then commenced as follows; but were only rendered fully satisfactory in the taking, when I had rigged up a cross plank and rope holdings, to prevent the otherwise inevitable sliding away of myself from the instrument, by reason of the steep slope of the passage. The index-correction above given was determined by two series of star observations the same night, one of them giving -1° 11′ 0′′ and the other -1° 10′52′′. CIRCULAR CLINOMETER. March 9.-To prepare the instrument for this work, I made it a new and longer foot, cutting up its former mahogany 50-inch foot into three pieces, and fastening them to the lid of the long box of the reference-scale in such a manner, by means of powerful screws, that a joist-shaped stand was formed of the following size, Total length of foot, or beam, Length between two longitudinal bearing points, Breadth between the line of the two longitudinal Vertical depth of beam through the 115 inches of its middle length, To the above were further fastened four angular lamp-holding blocks, two of them acting when beam was used face west, and two face east; while the whole structure was prevented from slipping when on the incline, by a rope fastened to a wooden anchor, and placed in a ramp-hole above it. This arrangement was found to work well; the level and tangent screws were easy to turn, and the verniers to read off. (See Plate I., or Frontispiece.) The observing method followed was, to take a |