AND INSTRUMENTS AT MUNICH. 511 
temperature (which though much less in the magnetic observa- 
tory than in the open air, still forms a sensible daily period), 
currents must have been produced in the air inclosed with the 
magnets in the bell-glasses, differing according to the times of 
the day and the position of the bell-glasses relatively to ex- 
ternal changes. 
In order to remove this cause I fastened strips of glass under 
the bell-glasses so as to protect the magnets from the influence 
of currents of air, and observed anew. 
[Here follows a table of observations. | 
Even this insufficient protection diminished the influence of 
the currents of air; the experiments next detailed show the suc- 
cess of a more careful protection in restoring the accordance of 
the different instruments, and the degree of exactness to which 
the small movements of two magnets so protected coincide. 
JuNE 26.—Comparison of Apparatus 1. and II. 
3 App. | App. A App. | App. : App. | App. 
Time. | P| Ph ||| Time. | EE | re, |] Time. te | Wet. 
a a bean. As 
36 0131-0 |-01 ||9 4 15 | 32-75|/4005 | 10 4 30/932 | 00 
15 | 31-0 | —0-2 30 | 32-75 | 0-05 45 | 232 | 0-0 
30 | 30-95 | —0-15 45 | 32-4 | 0-0 5 0 | 23-25 | —0-05 
45 | 30-95 | —0-15 5 01325 |—0-05 15 | 231 | 40-05 
37. «0 | 308 |—0-1 15 | 328 | 0-0 30 | 23-25 | 40-05 
15 | 30-7 | —0-05 30 | 32:9 | 0-0 45 | 23°35 | 0-05 
30 | 305 | 0-0 45 | 327 | 0-0 6 0) 23°35| 401 
45 | 30-45 | +005 6 0| 324 |—O1 15 | 23-35 | —0-5 
38 0 | 30-4 |—0-05 15 | 323 |—O1 30 | 23:35 | —0-5 
15 | 30°35| 0-0 30 | 32-0 |+0-05 45 | 23-1 | —05 
30 | 30:35| 0-0 45 | 31:9 | 0-0 7 0| 23-45 | +01 
45 | 30-4 | 0-0 7 0/317 | 00 15 | 23-4 | 0-0 
39 0/304 | 00 15 | 31-4 |—0-15 30 | 23-4 | 40-05 
15 | 305 | 0-0 30 | 31-2 |—0-1 45 | 23:5 | 40-1 
30 | 306 |—0-1 45 | 31:3 |—0-1 8 0 | 23-4 |+0-05 
45 | 306 | —0-05 8 0|310 | 00 15 | 23-4 | 0-1 
40 0/307 |—0-1 15 | 305 |401 30 | 23-4 | —0-1 
15 | 305 | .0-0 30 | 30-4 | | 0-0 45 | 23-35 | —0-05 
30 | 30-45) 0-0 45 | 305 | 0-0 9 0/233 | 0-0 
45 | 30-45| 0-0 9 0/305 |4005 || 11 3 0 | 16-4 |40-25 
41 0 | 30-45! 0-0 15 | 30-4 |—o-1 15 | 16-45| 40-2 
15 | 30-45 | —0-05 30 | 30°55 | —0-05 30 | 16-35 | 40-15 
30 | 30-45 | —0-05 45 | 30-45 | —0-05 45 | 16-4 | +02 
45 | 30-65 | —0-05 10 0 | 30-45| +.0-05 4 0 | 1635} 402 
42 0/308 |-01 |10 3 0) 233 |—O-1 15 | 16-35 | 10-25 
15 | 31-0 | 0-2 15 | 23:0 |401 30 | 16:3 | 10-2 
30 | 31-4 | 041 30 | 231 | 00 || 1256 0 | 11-65) 4035 
45 | 31-6 |—0-05 45 | 23-05 | 0-05 15 | 11-7 |+403 
43 0 318 |—O1 4 0/230 | 00 30 | 11-7 | +03 
23:25 | — 0-05 45 | 11-65 | 4-0-35 
