170 EIGHTH REPORT 1838. 



Horizontal intensity in Limerick, referre'd to Dublin 



October, 1834. Cyl. L a Int. = 1 -0075 



— — — LA — = 1-0015 

 July, Aug. 1835. —Re — = 1-0005 



— — — — Rrf — =1-0098 

 Aug. Sept. 1835. — L« — = 1-0039 



— — — — lib — = 1-0055 

 Nov. Dec. 1835. — L« — =1-0001 



— — — — LZ»— = 1-0021 



Mean = 1*0039 



Now, the comparison of Dublin with London and with Li- 

 merick being each the mean of eight separate comparisons, 

 while that of Limerick and London is deduced from four only, 

 we have (see Fifth Report, p. 133.) 



A = 2B = C. 



Hence the formulae of page 134 become 



4(a^+c,2)+l' ^ ^{a^ + c^) + i> 

 but a=-9390, Z» = -9460, c=l-0039j 



c, = -=l-0075, e,— c=:-0036: 



and, substituting these values, 



8.r=+'0009, 8y=-'00l7} 

 .r=a + Sa^ = -9399; 

 j/ = b + ht/ = '944S. 



The numbers in the 6th column of the following table are 

 deduced from those of the 5th, by multiplying by one or other 

 of these numbers, according as the station has been compared, 

 in the first instance, with Dublin or with Limerick. 



It will readily appear, from the principles laid down in pages 

 95 et seq., that the iveights of these determinations are ex- 

 pressed by the formulae 



X=A + #C£;, Y=B + . ^C 



Ba^+C ^ ^Aa^ + Cc^' 



