OF ARTS AND SCIENCES. 

 The distance of the mirror from the scale was 1797 rams. 



417 



Substituting these values in (B.), we get 



^=1092495; 



and combining with the value of MH, 



H=z \ — z= 1.6444 



V 1092495 



(;') Determination of the Dip. 



Six measures for each component were made, with the following 

 results : — 



VOL. XIII. iN.S. V.) 



27 



