Or 
DIP AND INTENSITY. 51 
3. Captain King’s Observations of Dip and Intensity. 
Captain King, having hitherto made known his observations 
with the same cylinder in the years 1826 to 1830 only by com- 
municating them to M. Hansteen, from whom he received the 
apparatus, has now given permission to Captain Fitz-Roy to 
publish them with his own. I have already noticed the great 
loss of magnetism which took place in this cylinder during Cap- 
tain King’s voyage, and the care with which that officer availed 
himself of every opportunity of ascertaining, by direct obser- 
vation, the proportion of the loss sustained in separate portions of 
the voyage. There are twelve stations of observation on the east 
and west coasts of South America, besides three stations in ports 
of the Atlantic on the outward voyage. By the practice of repeat- 
ing observations at the same station at distant intervals, the South 
American stations are so linked together and connected, that by 
adopting a method similar to that used in determining longitudes 
by means of chronometers, we may compute the intensity at all 
the South American stations referred to and dependent on the 
force at Rio de Janeiro; regarding Rio in the same light as a first 
meridian is considered in determinations of longitude. We may 
then make Rio the means of connecting the whole series with 
Europe ; for which it is remarkably well suited, the intensity there 
having been determined, independently of Captain King, by 
four observers of different nations, whose results are extremely 
accordant. 
The dip observations of Captain King were communicated, in 
occasional correspondence during the voyage, to M. Hansteen, 
who computed them by Mayer’s formula, and arranged them in 
a table, of which a copy was given by Captain King to Captain 
Fitz-Roy, and is printed in the next page. At some of the sta- 
tions Captain Fitz-Roy also observed the dip in the subsequent 
voyage, and, as will be seen, the results of the two observers 
sometimes differ considerably. This may have been caused, either 
by instrumental or other error of observation, or by actual differ- 
ences of dip existing in different localities at the same station, 
