520 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1721. 



do it, would give us an account of the variations they have lately found in 

 their voyages from Peru and Chili to China; and that the Spaniards would do 

 the same for the north part of that great sea through which they return from 

 the Manillas to New Spain With these helps, having three points in each 

 curve, we might be enabled with tolerable certainty to complete the system of 

 the magnetic variations, which I was forced to leave unfinished, as to this part 

 of the ocean, in my general chart, for want of the requisite observations. 



The following is the account extracted from Capt. Rogers's Journal, where 

 the first column gives the correct latitude of the place; the second, the longi- 

 tude west from London, as estimated by reckoning; and the third, the varia- 

 tion, which in this whole tract is easterly. 



Variations observed in the Great South Sea, from the South Cape of Calefornia 

 to the Island of Guana or Guam, one of the Ladrones, 



January 

 1709- lO 



12 



15 



20 



25 



30 



Feb. 



Lat. correct 

 every day 



Lonii:. west 

 from London 



22® 16' 



21 18 



20 24 



19 25 



18 56 



18 



17 11 



16 32 



15 44 



15 



14 49 



14 36 



14 24 



14 14 



13 50 



13 29 



13 29 



13 22 



13 27 



13 32 



13 32 



13 36 



13 26 



13 26 



13 26 



13 26 



13 25 



13 41 



13 41 



114° 9' 



114 42 



115 15 



115 45 



116 24 



117 6 



117 30 



118 5 

 118 54 

 120 15 

 122 5 

 124 25 

 126 45 

 129 5 



131 23 



132 58 

 134 41 

 136 48 

 139 21 

 142 7 

 144 37 

 147 32 

 150 18 

 153 2 

 155 19 

 157 43 

 160 31 



163 



\65 18 



Variation 

 easterly 



c 



50 

 50 

 50 

 45 

 45 

 15 

 

 50 

 30 

 10 



50 



40 



45 



50 





 10 

 15 

 25 

 30 

 40 

 50 





 10 

 25 

 30 

 50 





 20 



Island of Guana in sight. 



