306 DESCRIPTION OF GARNETT's 



N. B. If the distance extend beyond the Chart, which can 

 seldom happen in practice, it will require two operations as in 

 this instance. (Or it mav be performed at once on the general 

 Chart.) 



1st. Set the center C of the Index on the left side of the Cen- 

 tral Meridian (because sailing from the Equator) to 2° 30' diff. 

 of longitude, and on the given parallel of latitude 42° 25'. 



2nd, Extend the distance line on a 5 point course, to 2° 30' 

 diff. of longitude on the right hand of the Central Meridian, and 

 the first latitude will be found 44° 48' N. diff. of longitude 5° 

 East; and distance 258 miles; which writedown as under, for 

 the first operation. Then set the Index C to the last found 

 latitude, and the distance line on a 5 point course will extend 

 from 1° 40' diff. longitude on each side, to the given latitude 

 of 46° 20', and measure 167 miles; which added as under to 

 the first found distance and difference of longitude, gives the 

 whole distance and difference of longitude. 

 Lat. sailed from 42° 25' longit. 15° 6' W. course N. 5 pts. E. 



To latit. 44 48 diff. long. 5 E. distance 258 miles, 

 To latit. 46 20 diff. long. 3 '20 E. distance 167 miles. 



Gives the required diff. longitude 8° 20' E and dist. 425 miles. 



CASE IV. 



Given the Latitudes of two Places, and the Distance between them, 

 to find the Course and Difference of Longitude. 



EXAMPLE. 



A ship from St. Alban's Head, in latitude 50° 35' N. and 

 longitude 2° 5' W. sailed 171 miles upon a direct course be- 

 tween the S. and W. and by observation is found to be in lati- 

 tude 48° 26' N. required the course steered, and longitude 

 come to? 



1st. Set the center C of the Index on the given parallel of 

 latitude 50° 35' (on the right hand, because sailing towards the 

 Equator) and turn the distance line until the given distance 171 



