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Q: Which cross staff includes two identical- diameter cylinders stacked one on top of the other?
  • A. Open cross staff
  • B. Optical square
  • C. French cross staff
  • D. Adjustable cross staff
Correct Answer: Option D - Adjustable cross staff– The adjustable cross staff consists of two cylinder of equal diameter placed one on top of the other. Both are provided with sighting slits. The upper box carriers a vernier and can be rotated relatively to the lower by a circular rack and pinion arrangement actuated by a milled headed screw. The lower box is graduated to degrees and sub-divisions. It is, therefore, possible to set out any angle with the help of this instrument.
D. Adjustable cross staff– The adjustable cross staff consists of two cylinder of equal diameter placed one on top of the other. Both are provided with sighting slits. The upper box carriers a vernier and can be rotated relatively to the lower by a circular rack and pinion arrangement actuated by a milled headed screw. The lower box is graduated to degrees and sub-divisions. It is, therefore, possible to set out any angle with the help of this instrument.

Explanations:

Adjustable cross staff– The adjustable cross staff consists of two cylinder of equal diameter placed one on top of the other. Both are provided with sighting slits. The upper box carriers a vernier and can be rotated relatively to the lower by a circular rack and pinion arrangement actuated by a milled headed screw. The lower box is graduated to degrees and sub-divisions. It is, therefore, possible to set out any angle with the help of this instrument.