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( 5 ) NOTE:--Double bases give ranges in double yards, e.g., working with a double base or four cords, the drum reads 1,500. The range, therefore, is 1,500 yards multiplied by 2 (or 1,500 x 2) or 3,000 yards. Caution. (a) No ranges beyond 1,000 yards should ever be taken with a half base, that is, with one cord. (b) No ranges beyond 1,500 or 1,600 yards should ever be taken with an ordinary, or 25 yard, base, that is with two cords. (c.) Ranges above 1,500 or 1,600 yards should be taken with a double base, that is utilising the whole four cords (50 yards). Exceptional Cases. 23.--A 25 or 50 yard base may not be obtainable, then a 12 1/2 yard cord (or half base) must be used, but the difficulty of getting good ranges is very much increased as the very slightest movement of either No. 1 or No. 2 will be magnified owing to the short cord employed. 24.--With experts the instruments can be used with- out the telescopes, working fairly well and giving satisfactory results. NOTE:--When the telescope is not used, the shutter is drawn to cover the openings of the telescope, and the observer then uses the peephole. Speed of Observation. 25. Trained observers ought to be able to take any range in 15 to 20 seconds, provided always that the instruments are out of their cases and the cords stretched. 26.--After once picking up a moving object, five ranges a minute ought to be easily recorded. 27.--Finding the distance between two inaccessible objects can be easily executed by the Mekometer. T. A. MARTIN, CALCUTTA. FINIS.