YOL, XVII.] PHILOSOPHICAL TRANSACTIONS. 471 



by Mr. Burrows to be 1 1° 15' to the east ; in 1622, the same was found by Mr. 

 Gunter to be only 6° O' to the east; in l634, Mr. Gellibrand found it 4° 5' to 

 the east; in 1657, Mr. Bond observed that there was no variation at London ; 

 anno 1672, I observed it 2° 30' to the west ; and this present year l6y2, I again 

 found it 6° to the west. So that, in 1 12 years, the direction of the needle has 

 changed no less than 1 7 degi ees. 



At Paris, Orontius Finaeus, about the year 1550, reckoned it about 8° or 9' 

 east variation; in 164O, it was found 3° to the east; in J 666 there was no 

 variation there ,- and in 168I, I found it to be 2° 30' to the west. 



At Cape d'Agulhas, the most southerly promontory of Africa, about the 

 year 160O, the needle pointed due north and south without variation, whence 

 the Portuguese gave it that name; in 1622 there was 2° west variation: in 

 1675 it was 8° to the west ; and this year 1691, it was accurately observed to be 

 not less than 1 1° degrees to the west. 



At St. Helena, about the year 1600, the needle declined 8° to the east; in 

 1623, it was but 6° to the east ; in 1677, when I was there, I observed it ac- 

 curately on shore to be 40' east ; and now this year it was found about 1° to the 

 westward of the north. 



At Cape Comorin, in India, in the year 1620, there were 14° 20' west varia- 

 tion; in ]680, there were 8° 48'; but in 1688, it was no more than 7° 30'; so 

 that here the needle has returned to the east about 7° in 70 years. 



In all the other examples the needle has gradually moved towards the west, 

 and the places are too far asunder to be influenced by the removal of any mag- 

 netical matter, which may by accident be transplaced within the bowels or on 

 the surface of the earth. From these, and many other observations, it is evi- 

 dent that the direction of the needle is in no place fixed and constant, though 

 in some it changes faster than in others. And where for a long time it has 

 continued as it were unaltered, it is there to be understood that the needle has 

 its greatest deflection, and is become stationary, in order to return, like the 

 sun in the tropics. This at present, viz. 1692, is in the Indian sea, about the 

 island Mauritius, where is the highest west variation, and in a tract tending 

 from thence to the N.N.W. towards the Red Sea and Egypt. And in all 

 places to the westward of this tract, all over Africa and the seas adjoining, the 

 west variation will be found to have increased ; and to the eastwards thereof, as 

 in the example of Cape Comorine, to have decreased, viz. all over the East 

 Indies and the islands near it. 



In like manner, in that space of east variation, which, beginning near St. 

 Helena, is found all over South America, and which at present is highest about 

 the mouth of Rio de la Plata, it has been observed, that in the eastern parts of 



