250 Observations o;i ihc Dirtction and I7\fc7iisi'tij of the [Ariui, 



Class 1st. — Observations made from Madras to Trivandrum and bach 

 again. 



— 2t.l. — Observations made from TellicJiernj to 'rrivayulrum. 



— 3J. — Observations made from Madras to Ontjole and back again. 



Class I. 



If we now attentively examine Table II, in wliicli this arrangement 

 has been made for the first class of the cylinder T. G, T. No. i, we 

 perceive that the numbers in tlie column ditFerence," dec rease pretty 

 uniformly, in something like a geometrical progression, corresponding to 

 an arithmetical advance of the time, — until at Nag' acoil, we find that for 

 nearly a month, no alteration had taken pl.u-e in its intensity. If we 

 examine the observations with c\ lin lor T. G. T. No. 2, we find that pre" 

 cisely the same circumstance o 'curs ; and on examining T. G. T. No. 3, 

 it appears, that— with the ex<^eption of a difference of 10,00 seconds 

 caused by the cylinder havin^x been let fall, — during nine weeks its in- 

 tensity remained unchanged. If ilien it be admitted for cylinders Nos. 1 

 and 2, that they had arrived at a fixed state of intensity on the 25th 

 August; and that No. 3 had done so on the 2d August, it only remains, 

 that we should cancel the observations made previously to these dates, 

 and adopt those made subsequent thereto. One circumstance, however, 

 must be noticed with regard to cylinders Nos. 1 and 2, namely— that the 

 observations at eight stations made in the course of our onward march, 

 (between Negapatam and Palamcottah), have purposely been omitted ; 

 the cvlinders when at these places not having arrived at a fixed 

 state of intensity, the observations must necessarily be given up. With 

 regard to the two cylinders constructed by Mr, Caldecott, I have already 

 mentioned that I had submitted them to rather rough usage ; by which 

 their intensities had at once been reduced to the amount of several 

 seconds for performing 100 vibrations; my intention was to bring them 

 at once to a fixed state of intensity, for f can state with considerable 

 confidence, that when a needle is magnetized to saturation, its Joss of 

 magnetic intensity is due alone to the necessary violence ewployed in its 

 use. I have employed a cylinder which was magnetized to saturation 

 for a month — not touching it — without its having parted with any portion 

 of its magnetism ; but on applying the armature, and then again vibrating 

 it, a change of several seconds has immediately resulted. In confirma- 

 tion of these views, it will be noticed that on the return of cylinders 

 J. C. 1 and 2 to Trivandrum, after an absence of ten weeks, in which 

 they bad travelled over 1200 miles, 



s 



No. 1 had varied its intensity 0.40 > in performing 

 2 — 0.875 100 vibrations. 



