APPENDIX NO. XVI. 
435 
No. XVI. 
Magnetic Observations — Continued. 
Tables of hourly readings of the changes of the magnetic declina¬ 
tion at Rensselaer Harbor in 1854. 
The following observations for diurnal inequality do not include the 
term-day observations, which are given elsewhere. The mean time 
refers to the meridian of our winter quarters,—viz.: 4h. 42m. W. of 
Greenwich, or 5h. 22m. W. of Gottingen. The scale readings com¬ 
menced thirty minutes before and ended twenty-four minutes after the 
even hour, the observations being made every sixth minute; the scale 
readings in the second column of each table are therefore means of 
ten separate values. The third column contains the deviations from 
the mean direction, or the hourly changes in scale divisions. 
The scale reading 280 corresponds to a magnetic declination of 
108° 3' west of north; greater readings correspond to a smaller west¬ 
erly declination, and vice versd. One scale division was found to 
equal 0*79'. 
Hourly Changes of Magnetic Declination. 
Mean 
Time. 
January 10-11. 
January 13-14. 
Scalo Readings. 
Difference. 
Scale Readings. 
Difference. 
h. 
5 
296-80 
—11-93 
309-50 
+ 8-51 
6 
292.38 
— 7*51 
319-31 
— 1-29 
7 
287*42 
— 2-55 
331-20 
—13-19 
8 
278-75 
+ 6-12 
342-30 
—24-29 
9 
284*30 
+ 0-57 
359-40 
—41-39 
10 
288-00 
— 3-13 
358-85 
—40-84 
11 
295-35 
—12-48 
344-14 
—26-13 
12 
299-70 
—14-83 
349-34 
—31-33 
13 
307-90 
—23-03 
342-26 
—24-25 
14 
309-38 
—24-51 
346-20 
—28-19 
15 
308-18 
—23-31 
350-00 
—31-99 
16 
305-83 
—20-96 
362-20 
—44-29 
17 
298-30 
—13-43 
369-80 
—51-79 
18 
291-60 
— 6-73 
339-50 
—21-49 
19 
272-40 
+12-47 
317-80 
+ 0-21 
20 
266-70 
+ 18-17 
278-93 
+39-12 
21 
273-70 
+ 11-17 
268-07 
+49-94 
22 
253-73 
+31-14 
279-93 
+38-12 
23 
255-04 
+29-83 
267-15 
+50-86 
0 
270-53 
+14-34 
264-50 
+53-51 
1 
259-15 
+25-72 
243-20 
+74-81 
2 
265-70 
+19-17 
277-50 
+40*51 
3 
275-70 
+ 9-17 
296-18 
+21-83 
4 
296-20 
—11-33 
305-05 
+12-96 
Mean 
284*87 
318-01 
