ON COMPARING AND EEDUCING MAGNETIC OBSERVATIONS. 



535 



Solar hours 





These variations are expressed in one hundred-thousandths of the m.-g.-s. unit of 

 force. 



Curves, representing the numbers of this table, and complementary to 

 those of Plate I. of the British Association Report of 1 886, appear below : 



/c. 



•A) 



VKliTlCAb i'OI'.Ci;. 



Js-2 



Bombay Astronomical Hours. 



The scale is in m.-g.-s. units of force, 



they are, like their complements of declination and horizontal force, of 

 definite character, showing relatively large movements in the day hours 

 and quiescence at night, and they have a general resemblance to the 

 declination curves ; they also extend the evidence of the existence of a 

 luni-solar variation to the third magnetic element at Bombay, and thus 

 establish the fact in respect of the variations of magnetic force generally 

 at Bombay. 



On page 88 of the British Association Report for 1886 appears the 

 following note : ' In the curves for declination, as sent by Mr. Chambers, 

 the signs as given above are rever.sed.' The explanation is that the varia- 

 tions of the declination table are, as described, expressed in converted 

 tabulation excesses, but that increasing tabulations (or ordinates of the 

 registration curves) denote decreasing easterly declination, whilst in- 

 creasing ordinates of the curves of Plate I. denote increasing easterly 

 declination. The words ' Declination — East ' at the side of the table refer 

 to the absolute declination at Bombay. 



