MAGNETICAL OBSERVATION'S IN SCOTLAND. 105 



nished by 3' for the decrease of dip between 1835 and 1836,) is 

 71° 53'-3 ; deduced from tlie Scottish results it is 72° 01'-4 

 The actual observation was 71° 53'"5, agreeing in this case with 

 the Irish deduction. At Bangor the dip deduced from the 

 Irish results is 71° 32'-3, and from the Scotch 71° 41'-6 : the 

 observed dip was 71° 36'"7, being intermediate between the 

 two deductions. At Stranraer the deduction from the Irish 

 results is 7l° 3l'-9, and from the Scottish 7l° 40'*9 ; the observed 

 dip being 71° 40'"9, which in this instance corresponds with 

 the Scotch deduction. The discrepancy is not of greater 

 amount than may easily disappear on a slight modification of 

 the results in one or both countries, a modification which they 

 may be expected to receive from more multiplied and extended 

 observations. The true values of u and r are probably not 

 exactly the same in the two countries ; but it may be expected, 

 when observations shall be sufficiently multiplied, that the de- 

 ductions from the general results in both countries should 

 agree in giving the same dip for the frontier stations. 



We have hitherto no general series of observations of dip in 

 England ; but from the great pains which Captain James Clark 

 Ross has bestowed on its determination in London, we may 

 regard the result obtained by him in July 1835, viz. 69° 17''3, as 

 extremely free from instrumental error, and liable only to such 

 differences from the dip strictly due to its geographical position, 

 as may arise from local causes. The corrected dip for Sep- 

 tember 1836 would be about 69° 14'. The difference of dip 

 between the central station in Scotland and in London, com- 

 puted with the values of x and i/ i-esulting from the Scotch ob- 

 servations,is — 3°-075 which being deducted from 72° 17''3, leaves 

 the computed dip in London 69° 10''3. This is another con- 

 firmation that the Scotch results are near approximations, pre- 

 suming, as is probable, that the values of u and r are nearly the 

 same in England as in Scotland. In this instance the deduc- 

 tion from them is in defect; in the comparison with those from 

 the Irish results it is in excess. 



II. Intensity. 



§. Hi/ Professor lAoyiVs Statical Method. 



The observations by this method Mere made with the same 

 needle that was employed in determining the dip, viz. S (2). 

 The method itself is described in the Fifth Report of the British 

 Association, page 137, and more largely in the Transactions of 

 the Royal Irish Academy for 1836. 



It is important in all observations of intensity that the needle 



