494     M.  F.  Zollner  on  the  Origin  of  the  Earth's  Magnetism, 
troduced,  so  as  to  allow  free  access  to  the  instrument.  The 
observations  were  made  from  the  inner  space  of  the  small  ob- 
servatory, one  wall  of  which  was  broken  through  for  this  pur- 
pose ;  through  this  opening  the  mirror  of  the  pendulum,  shut 
up  in  a  separate  box  with  a  plane  glass  plate,  was  observed. 
I  now  take  the  liberty  to  communicate  an  observation  extended 
over  several  hours,  which  I  made  on  September  18,  1870,  du- 
ring the  evening  hours  from  6h  35m  to  10h  35m. 
Observation  with  the  Horizontal  Pendulum. 
Distance  of  scale  from  mirror  =3186  millims. 
Duration  of  a  vibration       .      =14* 444  seconds. 
With  regard  to  the  above-mentioned  time  of  vibration  of  0*25 
second,  we  calculate  that  a  millimetre-division  on  the  scale  cor- 
responds to  a  deviation  of  00097063  second  of  an  arc  of  an  or- 
dinary pendulum.  The  numbers  given  in  the  Table  indicate 
the  readings  of  the  values  of  the  elongations. 
Leipzig,  September  18, 
187C 
>. 
No. 
Time. 
Reading. 
No. 
Time. 
Reading. 
No. 
Time. 
Reading. 
1. 
h    m 
6  35 
»»4 
15. 
h   m 
7891 
80-9  j  7yy 
29. 
h   m 
7  52 
79-81  „,., 
82-4  J811 
2. 
™}m 
16. 
7  35 
7?;o}8o-3 
30. 
«!*■» 
3. 
"Bfw 
17. 
lit  j80"7 
31. 
&}■» 
4. 
«}*■ 
18. 
82}«* 
32. 
8    0 
STIW* 
5. 
in}™ 
19. 
85}«* 
33. 
SK}«* 
6. 
fH}m 
20. 
sa«-o 
34. 
8    2 
&}•» 
7. 
III  }789 
21. 
7  35 
»}■« 
35. 
808  I  81-9 
820/8iy 
8. 
78-1  179-1 
801  j?yi 
22. 
8^}80-8 
36. 
SK}«* 
9. 
78  2-1 
80-3 j75^ 
23. 
m}810 
37. 
^K1 
10. 
Sol}79'6 
24. 
7  38 
8?;0}so, 
38. 
8    4 
&}•" 
11. 
787 1797 
80-6/ 7y/ 
25. 
7  50 
Slf80'8 
39. 
10    0 
SIS}** 
12. 
6  53 
790  V  79-7 
80-5  f  '  •  ' 
26. 
827}8l-° 
40. 
SS}« 
13. 
III}™'6 
27. 
m}81*0 
41. 
10  35 
83-9  1  ft-  , 
86-4  ;851 
14. 
78-91  7q.6 
8o-3  r7yb 
28. 
«}■" 
42. 
86-3  }85<1 
These  numbers  will  be  sufficient  to  prove  the  great  sensitive- 
