.NAVIGATION CHART, &C. 305 



found on the Index will be 340 miles ; — and the course cross- 

 ed by the parallel of latitude, will be N. 42 3-4 degrees, ei- 

 ther East or West; according as the latter place is Eastward or 

 Westward of the former. Q. E. I. 



N. B. When the differences of latitude and longitude are 

 great, as it often happens in this Case, the course and distance 

 may be found sufficiently accurate for practice on the general 

 Chart of this projection. But in Great Circle Sailing the angles 

 of position should be found by Spherical Trigonometry, 



CASE II. 



Given one Latitude, Course and Distance, to find the other 

 Latitude, and difference oj Longitude. 



EXAMPLE. 



A ship from latitude 52° 10' N. and longitude 35° 6' West, 

 sails N. W. b. W. 229 miles; required the latitude and lon- 

 gitude arrived at. 



1st. Lay the centre C of the Index (to the left side) on the 

 parallel of latitude 50° 10' and turn it about until the parallel 

 passes through the 5 point course; then slide it on the paral- 

 lel until the distance 229 miles subtends nearly an equal dif- 

 ference of longitude on each side the Central Meridian ; which 

 will be found 2° 40' on each side, or 5° 20' diff. of longitude, 

 when the distance will also reach the parallel of latitude 54° 17'; 

 for the latitude arrived at. Q. E. I. 



CASE III. 



Given both Latitudes and the Course; to find the Distance, and 

 Difference of Longitude. 



EXAMPLE. 



A ship sails N. E. b. E. from latitude 42° 25' N. and loiv 

 gitude 15° 6' W. and then rinds by observation she is in lati- 

 tude 46° 20' N. ; required the distance, and present longitude 



