CONTENTS. 



I. MEMORANDUM ox THE MAGXETICAL OBSERVATIOXS MADE DURING THE VOYAGE. By Sir FREDERICK 



EVANS, KC.B., F.R.S., Hydrographer, ....... 1 



II. MAGXETICAL IXSTRUCTIOXS, 1872, ........ 8 



Addenda to Magnetical Instructions of 1872, .... 21 



IIL ABSTRACT OF MAGNETICAL OBSERVATIONS DURING THE VOYAGE, .... 23 



Declination or Variation of the Compass. 

 Inclination or Dip. 

 Total Force (British Units). 

 IV. ABSTRACT OF MAGNETICAL OBSERVATIONS MADE AT LAND STATIONS, PREFACED WITH DESCRIPTIVE 



REFERENCES TO THE POSITIONS (OBSERVATION SPOTS) OF THE INSTRUMENTS, ... 45 



Declination or Variation of Compass by Declinometer and Compasses. 

 Inclination or Dip. 



Absolute Horizontal Force (British Units). 

 V. ABSTRACT OP VARIATIONS OF THE COMPASS OBSERVED AT SEA, ..... 74 



VL ABSTRACT OF OBSERVATIONS WITH Fox CIRCLES, ...... 100 



Inclination or Dip. 

 Total Force (British Units). 

 Tables of Corrections for Observations made at Sea 



1. Declination. Coefficients of Standard and Fox Compasses, .... 274 



Computed Deviations of Standard Compass, ..... 276 



Computed Deviations of Compass in Fox Circle position, . . . .278 



2. Inclination. Correction for direction of Ship's head, ..... 280 



3. Correction of X. for values of . , .,, ..... 282 



A M 



4. Correction -j- for values of d, . . . . k . 290 



5. Total Force. Tables of Equivalent Weights, ...... 291 



6. Correction for direction of Ship's head, ..... 296 



7. Abstract of constants of the Ship's Magnetic Force, ..... 298 

 VII MEMORANDUM ON THE METEOROLOGICAL OBSERVATIONS MADE DURING THE VOYAGE. By Staff- 



Commander TIZARD, R.X., . . . . . . . . 300 



VEIL ABSTRACT or METEOROLOGICAL OBSERVATIONS, ....... 305 



Appendix A. THE PRESSURE ERRORS OF THE CHALLENGER THERMOMETERS. 



By Professor P. G. TATT, MA., Sec. R.S.E., Professor of Xatural Philosophy in the University of Edinburgh. 



Received 1st July 1881. 



Appendix B. ON THE PETROLOGY OF ST. PAUL'S ROCKS (Atlantic). 



By Professor A. REXARD, F.G.S. 



Received 30th October 1879. 



