PEOFESSOE  PLCCEIEE  ON  THE  MAGNETIC  INDUCTION  OF  CEYSTALS.  569 
Table. 
Number  of  oscillations. 
18 
Number  of  seconds  required. 
Axis  2B  vertical. 
169'! 
17ol 
169] 
Mean  169*33 
14 
12 
Axis  2C  vertical. 
. . . . 1^0*5 
Axis  2A  vertical. 
Mean  159. 
To  control  the  constancy  of  the  current  during  the  observations,  in  each  suspension 
the  number  of  seconds  corresponding  to  the  first  and  last  half  number  of  oscillations 
was  separately  marked ; but  the  number  of  seconds  having  been  found  in  all  cases  equal 
to  half  the  total  number,  I thought  it  not  necessary  to  note  it  here.  Finally,  the  first 
observation  was  twice  repeated;  we  found  166*5  instead  of  169*5,  indicating  a small 
increase  of  the  magnetic  power. 
The  ratio  of  the  three  mean  numbers  of  the  Table  being  independent  of  the  intensity 
of  the  current,  the  next  day  we  determined  by  observation  in  a more  peculiar  way  the 
ratio  of  the  first  and  second  number,  and  afterwards  the  ratio  of  the  first  and  third. 
In  both  cases  we  got  small  differences.  Accordingly,  the  observation  of  the  first  case 
admitting  the  greatest  accuracy,  we  retained  the  first  mean  number  169*33;  instead  of 
the  second,  160*5,  we  adopted  159*75  ; instead  of  the  third,  159,  we  adopted  160*2. 
The  square  of  the  time  of  one  oscillation  concluded  from  the  corrected  Table  is  in 
the  three  cases 
88*51, 
0^=130*19, 
0^*  =178*22. 
Putting 
A^=400,  B^=160,  e=100. 
we  get 
A^+C^=500,  A*+B^=560,  B^+C^=260; 
therefore 
^ -5-649, 
^ m 
1-459. 
The  sum  of  the  last  two  numbers,  equal  to 
5*760, 
4 F 2 
