Def. 34. Fig. 10. The angle ZCE is the Zenith Distance of E.

Def. 35. Fig. 6.

Def. 36. Fig. 6.

Def. 37. Fig. 6. meridian HNO.

Def. 38. Fig. 7. upper meridian HZO.

ZAN, ZBN, and HZON are Vertical Circles.

ZAN is the Prime Vertical.

Civil Time begins when the sun is on the lower

Def. 39. Fig. 11. See Page 16 "Theory" for the explanation of the figure. The angle CPA is the Sidereal Time.

Def. 40. Fig. 11. The angle CPM is the Mean Time.

Def. 41. Fig. 11. The angle CPT is the Apparent Time.

Def. 42. Fig. 11. The angle TPM is the Equation of Time.

Def. 43. Fig. 11. CPx is the Hour Angle of x.

Def. 44. Fig. 6. The arc ZE is the Complement of HE; and the angle ZAE is the Complement of HAE.

Def. 45. Fig. 6. The arc EZO is the Supplement of HE; and the angle EAO is the Supplement of HAE.

Rotation No.

Exn. 9.

Port of.........

ADJUSTMENTS OF THE SEXTANT.

The applicant will answer in writing, on a sheet of paper which will be given him by the Examiner, all the following questions, numbering

his answers with the numbers corresponding to the questions.

1. What is the first adjustment of the sextant?

2. How do you make that adjustment?

3. What is the second adjustment?

4. Describe how you make that adjustment?

5. What is the third adjustment?

6. How would you make the third adjustment?

7. In the absence of a screw how would you proceed?

8. How would you find the index error by the horizon?

REMARKS.-The Examiner may take a sextant and ask the Candidate to point out the different parts of it, and show how he would use it.

ANSWERS TO THE ADJUSTMENTS OF THE SEXTANT.

1. The index glass must be perpendicular to the plane of the sextant. 2. Place the index near the middle of the arc, and look into the index glass so that you can see both the arc and its reflection; if they be in one line, the glass is perpendicular, but if not in one line, they are brought so by gently moving the screws in the frame upon which the glass stands.

8. The horizon glass must be perpendicular to the plane of the sextant.

4.—Place the zero of the vernier on O on the arc, hold the instrument obliquely, with its face upwards, and look at the horizon; if the true and reflected horizons be in one line, this adjustment is perfect; but if not, they must be brought in one line by gently moving a screw at the back of the glass.

5.—The index and horizon glasses must be parallel when the index is at O.

6. Place the index at Ɔ, and hold the instrument vertically, look at the horizon, if the true and reflected horizons be in one line, this adjustment is perfect; but if they be not in one line, move a screw at the back of the horizon glass till they are.

7.—I would find the index correction, or, as it is called, the index

error.

8.-Hold the instrument vertically, and, looking at the horizon, I would move the tangent screw until the horizon in both parts of the horizon glass form one line; the reading is the index error.

9. How is it to be applied?

10. Place the index at error of

it, and leave it.

minutes to be added, clamp

NOTE.-The Examiner will see it is correct.

11.-The Examiner will then place the zero of the vernier on the arc, not near any of the marked divisions, and the candidate will read it.

NOTE. In all cases the applicants will name, or otherwise point out, the screws used in the various adjustments.

NOTE to 10 and 11.-When the Examiner is satisfied that the candidate can read the arc of the sextant both on and off the arc, it will be sufficient to place his initials against 10 and 11 on the paper containing the answer. The above completes the examination of Second and only Mates.

In addition to the above, First Mates and Masters will be required to state in writing :

12.-How do you find the index error by the sun?

13.-How is the same applied?

14. What proof have you that these measurements or angles have been taken with tolerable accuracy?

REMARKS.-The Examiner may take the sextant in his hand and ask the candidate to point out the index glass, horizon glass, arc, vernier, tangent screw, and so on. He may also ask him how he holds the sextant when he makes the several adjustments, and uses it.

9. To be added when the reading is off the arc, and to subtract when the reading is on the arc.

12. I would place the index at about 82 on the arc, and, looking at the sun, two suns will be seen; bring their upper and lower limbs in exact contact, read off and mark down, then place the index at about 32′ off the arc, or to the right of O, bring the lower and upper limbs in contact as before, read off and mark down; half the difference of these two readings will be the index error.

13.-It is to be added when the greater reading is off the arc, and subtracted when the greater reading is on the arc.

14.—I would add the two readings together, and divide the sum by 4; if the measurements be correct, the result should be nearly equal to the semi-diameter for the day, as given in the Nautical Almanac. If they do not so agree, I would repeat my observations until they do.

J