120 DR. W. G. DUFFIELD, MESSRS. THOS. H. BURNHAM AND A, H. DAVIS ON 
Arc-length in mms. Arc-Length in inms. 
Fig. 11. From Table VII. 
probably real; no reason is known for the discrepancy between the two sets of 
readings in hg. 12. 
.\rc-length in mms. 
Fig. 111. From Table VIII. 
O 
