and  the  Magnetic  Relations  of  the  Heavenly  Bodies.        463 
same  time  new  laws  of  the  solar- diurnal  change  have  been  esta- 
blished, which  are  deemed  to  be  incompatible  with  the  supposi- 
tion of  a  thermic  agency.  There  has  been,  accordingly,  a  ten- 
dency of  late  to  recur  to  the  hypothesis  that  the  sun  and  moon 
are  themselves  endued  with  magnetism,  whether  inherent  or  in- 
duced j  and  it  is  therefore  of  some  importance  to  determine  the 
effects  which  such  bodies  would  produce  at  the  earth's  surface, 
and  to  compare  them  with  those  actually  observed. 
"  I  have  endeavoured,  in  what  follows,  to  solve  this  question  on 
the  assumption  that  the  supposed  magnetism  of  these  luminaries 
is  inherent.  The  result  will  show  the  insufficiency  of  the  hypo- 
thesis to  explain  the  phenomena — and  will  therefore  bring  us  one 
step  nearer  to  their  explanation,  by  the  removal  of  one  of  their 
supposed  causes." 
The  results  of  the  analytical  research  which  follows  are  summed 
up  by  the  author  in  the  following  words  : — - 
"  From  the  foregoing  we  learn  : — 
"  1 .  That  the  effect  of  a  distant  magnetic  body  on  each  of  the 
three  elements  of  the  earth's  magnetic  force  consists  of  two 
parts,  one  of  which  is  constant  throughout  the  day,  while  the 
other  varies  with  the  hour-angle  of  the  luminary. 
"  2.  Each  of  these  parts  varies  inversely  as  the  cube  of  the 
distance  of  the  magnetic  body. 
"  3.  The  variable  part  will  give  rise  to  a  diurnal  inequality, 
having  one  maximum  and  one  minimum  in  the  day,  and  subject 
to  the  condition 
"  The  third  of  these  laws  does  not  hold,  with  respect  either  to 
the  solar  or  to  the  lunar-diurnal  variation.  Thus,  in  the  solar- 
diurnal  variation  of  the  declination,  the  changes  of  position  of 
the  magnet  throughout  the  night  are  comparatively  small,  and 
do  not  correspond,  with  change  of  sign  only  (as  required  by  the 
foregoing  law),  to  those  which  take  place  at  the  homonymous 
hours  of  the  day. 
"  The  phenomena  of  the  lunar- diurnal  variation  are  even  more 
opposed  to  the  foregoing  law,  the  variation  having  two  maxima 
and  two  minima  of  nearly  equal  magnitude  in  the  twenty-four 
lunar  hours,  and  its  values  at  homonymous  hours  having  for  the 
most  part  the  same  sign.  Hence  the  phenomena  of  the  diurnal 
variation  are  not  caused  by  the  direct  magnetic  action  of  the 
sun  and  moon." 
In  the  discussion  of  this  paper*,  Lamont  agrees  perfectly 
with  these  results,  and  concludes  his  account  with  the  following 
words : — 
"From  this  Mr.  Lloyd  draws  justly  the  conclusion  that  the 
*  Berliner  Berichte  der  phys,  Ges.,  1858,  p.  592. 
