Εικόνες σελίδας
PDF
Ηλεκτρ. έκδοση

longitude 177° 18' W, what is (a) the difference of latitude, and (6) the difference of longitude, expressed in arc, between the two places?

(8) Define course, distance, and departure. Illustrate your answer by a sketch, and mark the different parts of the triangle with the proper names.

(9) (a) How is the circumference of the compass card divided? (5) Name the quadrantal points. (c) What does the lubber's point indicate?

(10) A steamer from Pointe aux Barques, in latitude, 44° 2' N, runs a distance of 62' true north. Find her latitude in.

(11) (a) Name the points, half points, and quarter points contained between N 45° E and S 11° 15' W.

(6) How many degrees are contained between the points N by W W and SW W?

(12) (a) By what compass should the ship's course be set and all bearings taken? (6) Name the requirements of a perfect compass.

(13) (a) Describe the effect of the pole of one magnet, either red or blue, on the poles of another magnet. (6) Considering the earth as a magnet, in what hemisphere is the blue pole situated?

(14) What do you understand (a) by the magnetic meridian? (6) by the magnetic equator? (c) Do the terrestrial and the magnetic equator coincide?

(15) What causes the magnetic needle to be deflected from the magnetic north and south, and why is this deflection different for different positions of the ship?

(16) (a) What is the name given to the phenomenon of the magnetic needle being deflected from the true meridian? (6) Is the amount of this deflection the same all over the world? (c) Is it constant, or does it change with time?

(17) Where is the amount of variation to be found?

(18) State the amount of variation (a) in the neighborhood of the Apostle Islands, Lake Superior, (6) near Sand Beach, Lake Huron.

(19) In reference to magnetism, what do you understand by soft and hard iron?

(20) State whether the semicircular error of the compass is caused by the magnetism of the hard or soft iron of the ship.

(21) (a) What name is given to the deviation caused by the magnetism of the horizontal soft iron of the ship? (6) In what direction of the ship's head is this deviation greatest?

(22) Describe the general principles on which to compensate a compass. Illustrate by sketch, using a different figure than the one given in the text.

(23) Name the principal errors of the compass that should be compensated, and state how these errors in reference to compensation are divided and denoted.

(24) How would you compensate that part of the semicircular error denoted by C, assuming the ship not to be equipped with a compensating binnacle?

(25) Describe how that part of the semicircular error denoted by B is compensated without a compensating binnacle.

(26) Is it necessary that the magnets used for compensating B and C should be fastened on deck? If not, state where and how they should be placed.

(27) What means are used to compensate the quadrantal deviation?

(28) Describe the nature of a Flinders bar, and state for what purpose it is used.

(29) What do you understand by subpermanent magnetism of an iron ship, and state when and how it is acquired?

(30) State briefly the main object of compensating a compass.

Oraries , Peter
Charles

LAKE NAVIGATION

(PART 2)

EXAMINATION QUESTIONS (1) Describe briefly each of the methods used to determine the deviation of the compass when in port.

(2) Give the rule to determine whether deviation is easterly or westerly.

(3) Is the deviation table that has been arranged for the standard compass applicable to other compasses in the same ship?

(4) How often is it advisable to test the accuracy of a deviation table?

(5) (a) Name the different kinds of courses. (6) Explain each clearly and illustrate your answer by a sketch.

(6) (a) How is a compass course corrected for leeway? (6) A ship sails an apparent course S E by S, wind E by N, leeway 21 points. Give the correct course.

(7) Draw a diagram showing 15° westerly variation and 17° westerly deviation, the compass course being N 48° E. Find by its aid the true course.

Ans. N 16° E.

(8) A ship steers by compass S W · W, wind S S E, leeway point, deviation 6° 45' E, variation 3° W. Show by a figure how the true course is found. Ans. S 60° W. (9) The course by standard compass is N 45° E, wind . NW, leeway point, deviation according to Table III, and variation 4° 37' W. Required the true course. Ans. N E.

(10) The true bearing from one port A to another B is, according to the chart, N 69° E. The wind is blowing from SE with a velocity estimated to produce 15 points leeway; the deviation is 2° 50' E, and the variation 14° 20' E. What course is the ship to steer by compass in order to reach B?

Ans. N 68° 42' E.

(11) The compass bearing of a distant object is S 17° W. The ship's head is NW by N, variation 17° W, deviation according to Table III. Find the true bearing,

Ans. S 19° E.

(12) A compass is brought on shore for the purpose of determining the deviation of the ship's standard compass, whereupon the ship is slowly swung around. The results of the simultaneous bearings taken are as follows:

[blocks in formation]

Required the deviation of the standard compass for each of these points.

(13) Obtain the course to steer by compass, the true course being NNW, variation 4o E, deviation 7° 15' E, leeway 1 point, wind W S.

« ΠροηγούμενηΣυνέχεια »