SPECIMEN EXAMINATION FOR SECOND MATE 



37 



Name the corrector indicated by each 

 letter on the sketch and state the type 

 of magnetism each is designed to cor- 

 rect. 



How can the brightness of the reflec- 

 tion from the horizon glass be varied in 

 a sextant? 



How is the master gyro-compass com- 

 pensated for permanent errors? Sup- 

 pose the master gyro heading is 278° 

 and it has been definitely established 

 (by azimuth, bearings, etc.,) that the 

 compass has a 2° easterly permanent 

 error, state how you would compensate 

 the master to read true. 



How do you determine the accuracy 

 of a ship's barometer, whether mer- 

 curial or aneroid? 



Why is mercury used in the barom- 

 eter in preference to other liquids? 



Make a rough copy of the sketch be- 

 low and on it label the following: "E- 

 Layer," "F-layer," "One Hop F," "Two 

 Hop F," "One Hop E," "Two Hop E," 

 and "ground wave." 



In taking a loran reading : 



(a) What will be the result of 

 matching a first sky wave with a 

 ground wave, or matching a first sky 

 wave with a second sky wave? 



(b) What precautions should be 

 taken to insure that the first pulse in a 

 train of pulses is not being overlooked? 



In the loran method of navigation: 



(a) What is the base line? 



(b) What is the base line exten- 

 sion? 



In using a loran chart, the lines on 

 the chart are for ground waves. Where 

 are the corrections to be found when 

 using sky waves? 



When sky waves are used for com- 

 puting loran lines of position, are they 

 more accurate close to the station or 

 far away from the station? 



What does blinking of a loran signal 

 indicate? 



How is a chronometer's accuracy 

 checked? 



What is the error of collimation of a 

 sextant? 



What is a ground wave? 



What is a sky wave? 



What is the critical range in loran 

 reception; why is it critical; and what 

 precautions must be taken with regard 

 to the use of signals? 



Explain the construction, principle, 

 and care of the barograph. 



Upon what 2 natural forces does the 

 directive force of the gyro-compass de- 

 pend? 



State briefly the routine inspection 

 and maintenance care which should be 

 given the master gyro-compass each 

 month. 



What are the markings of the hand 

 lead line? 



