524 DR. LAMONT ON THE MAGNETIC OBSERVATORY 
net was suspended in the experiments of vibration, i. e. 0°0007, 
we obtain 
absolute intensity = 1°9344 
— 0°000045 (¢ — 13°) 
— 0:000382 (¢ — 36° 50!) 
—0°004545 (T— 4":33) x 100. 
In reference to the following measurements, it must be noticed, 
that on the 23rd of October new deflecting magnets were 
applied to the differential instrument for horizontal intensity. 
These deflectors had not attained a steady magnetic condition, 
and lost a portion of their magnetism, partly equably, partly 
irregularly (the latter particularly when sudden rains set in) ; 
and in consequence it became necessary several times to bring 
them nearer the suspended magnet, otherwise the scale would 
have passed out of the field of view of the telescope. The whole 
loss in magnetic force from the 23rd of October to the 5th of 
December, amounted to about ;4,. On the 12th and 22nd of 
November sudden changes appeared to have taken place. On 
the 17th of November the magnets were brought nearer, so that 
the readings became 46 divisions less. 
In reference to the calculations, I must further remark, that a 
division of the differential instrument corresponds to a change 
of 0°0002 of the intensity; using this value all the intensities 
are reduced to division 40 of the differential instrument. The 
measurements were made at different hours of the day. 
Absolute 
Angle of deflection | Time of vibration | Tempe- |intensity re- 
and intensity. and intensity, rature. |duced to in- 
tensity 40, 
‘ a“ 
Nov. 11.| 87 0:5 41:3 | 43286 41-5 | +2-6 | 1-9312 
37 0:5 38-4 | 4:3326 38:5 | +51 1:9298 
12.| 36 593 38-7 | 43310 39°9 | 445 1-9309 
36 58:9 361 | 43366 37:5 | +66 1:9283 
13.| 86 56°3 48-4 | 4:3354 47°6 | +5:3 1-9282 
36 55:99 503 | 4:3354 504 | +5°3 19279 
36 57-2 47:2 | 4:3354 48:3 | +5°6 1:9280 
16.| 36 57:2 53:6 | 4:3326 51°8 +27 1:9284 
17.| 36 563 60-1 | 43309 59-7 | +2°3 1-9280 
Differential-instrument altered. 
20.| 36 55:2 11-1 | 43423 85 | +5-4 1:9331 
22.| 36 49°38 264 | 43407 26:7 | +63 1-9326 
23.| 36 49°8 33:7 | 43445 32°8 | +53 1-9294 
24.| 36 53°2 305 | 4:3448 32-2 +4-0 19285 
36 52% 36:5 | 43424 36:7 | +41 1-9289 
25.| 36 49:'2 47:9 | 4:3410 45°0 | +3°5 1-9288 
36 47°53 47-6 43408 47:0 | 44-2 1-9292 
