183D] 



Terr esf rial Magnetic Force in Southern India. 



225 



Face of Inst, east : axis direct -f- 8 10 + 8 15 -|- 7 54 f 8 6 



west 7 10 7 0 7 lo 7 3 



• invd. 8 15 8 0 - 7 25 7 1/ 



p-st 7 15 7 2> 7 4 7 8 



The mean = -f '2° 12' 52" + 14^ I i' 15" ^ 2° 14' 30" + 2° 12 l.V 



.•. Tiie ii ue dip — 2" 12' 2° io' 22" 



The above is one case out of many which occur, in whi -h although 

 large diiTer>uoes vtre fonn 1 iu fhe several sini/le readings, still the means 

 are coin.ddeni; utiicrcaies there are, houever, in which the means dis- 



agree : thus- 



Mean of Re;idings Meai^ of R^adin^s 



when af rest. when oscidating. DiTerence. 



N^^ale ;T.\,ve H = + 2" 4G' 4." + 2° 3r C° 15' 1 X" 



No. 3 = I 6 30 1 22 51 0 16 24 



TranqueburNj. 3 = 1 47 48 2 11 11 0 2^ 23 



Those r'^sults tom the ne'^d'es when vihntin::: appearing invariably- 

 more rousistpnt di-in fbose derived in the u-^ual way, I have not hesitated 

 to give tbetn tlie preference, and rejccl. the stition trv observations. 



The observations with the inten-iify needles r-^qaire hat little notice 

 Jie re, beyond the m'^ntion that th^y liave been uniform' v m ide by noting 

 the time of des ribing tbn first, second, and third hundred vibrations, com- 

 HK^ucing from an arc of 20 degrees on either side of the meridian. Add- 

 ed to this, it onlv remains to state th it the observations boih for dip and 

 intensity were uniformly' cotrmenc ^d between the hours of 9 -ind 10 in 

 the morning;, and finished at 2 or 3 in the afternoon. — We will now re- 

 sume our journey. 



Wele^t Ti-anquebar on the eveningof the 13th Auo-ust, and proceeded 

 to the southward, making observations every day (■^t distances of from 

 20 to 25 tniies), ani arrived at Trivandrum on the 2t)th August. Here 

 wehal leisure to examine our observations; and the result of it, as will 

 appear in tlie sequel, was not so satisfactory as could be wished : it ex- 

 hibited an nncertjinty in the dip observations at severd pl tces, to some 

 amount, and the intensity observations were not altog 'ther free from hi ime. 

 This determined me to re-observe onmy return liome ward, at those pla 'es 

 at which doubtful results had been obtained; and, having met with a clever 



