358 On the Diurnal Period of Terrestrial Magnetism. 



Geeenwich. 



Bombay. 



Time 



Intensity 







Intensity 



Time 



(astrono- 



(amperes 



Direction. 



Direction. 



(amperes 



(astrono- 



mical). 



io- 6 ). 







10~ 6 ). 



mical). 



h 





o 



o 





h m 







366 



4- 53 



- 67 



556 



12 



1 



398 



+ 36 



- 65 



442 



1 12 



2 



364 



+ 24 



- 65 



282 



2 12 



3 



282 



+ 14 



- 75 



125 



3 12 



4 



184 



- 2 



+ 



8 



4 12 



5 



128 



- 29 



+ 88 



92 



5 12 



6 



126 



- 72 



+ 85 



165 



6 12 



7 



136 



- 87 



+ 85 



229 



7 12 



8 



146 



-104 



+ 85 



253 



8 12 



9 



149 



-117 



+ 88 



261 



9 12 



10 



149 



-121 



+ 90 



251 



10 12 



11 



146 



-124 



+ 86 



231 



11 12 



12 



138 



-159 



+ 98 



211 



12 12 



13 



120 



-132 



+ 100 



201 



13 12 



14 



110 



-136 



+100 



188 



14 12 



15 



110 



-136 



+ 97 



177 



15 12 



16 



118 



-132 



+ 94 



165 



16 12 



17 



124 



-134 



+ 98 



152 



17 12 



18 



136 



-149 



+ 127 



132 



18 12 



19 



168 



-169 



+ 139 



181 



19 12 



20 



219 



+170 



-152 



223 



20 12 



21 



263 



+145 



-113 



348 



21 12 



22 



277 



+116 



- 90 



462 



22 12 



23 



289 



+ 80 



-76 



569 



23 12 



The table well repays a careful study. The Bombay ob- 

 servations on magnetic declination refer, as regards time, to 

 twelve minutes past each hour ; the observations at the same 

 place on horizontal force to fourteen minutes past each hour. 

 This is only one of the many little devices by means of which 

 the heads of magnetical observatories try to enliven the time 

 of those who want to compare their results. 



The direction of the currents is reckoned from the geogra- 

 phical north towards the west as positive, and towards the 

 east as negative. It is very remarkable how very nearly at 

 the same local hours the currents flow north and south at 

 Bombay and at Greenwich, namely at 4 in the afternoon 

 and between 7 and 8 in the morning. It is curious, more- 

 over, how very quickly the current turns through the meridian 

 at Bombay ; at 3 o'clock it flows at an angle of 15° from 

 the east, and at 5 already it flows due west, and remains 

 almost unaltered in direction till 5 o'clock in the morning. 

 At Greenwich the currents turn much less sharply, but they 

 always flow east when the currents at Bombay flow west, 



