RESULTS OF THE VOYAGE OF HALS. PENGUIN. 
349 
Considering the importance of a uniform system of exhibiting the value of the 
observer’s work in observations of similar nature, it was originally intended to adopt 
that of Professors Rucker and Thorpe, as explained in their “ Magnetic Survey of 
Great Britain ” (see ‘ Phil. Trans ,’ 1890). The difficulty then arose of there being no 
means for ascertaining the solar diurnal variations and effects of disturbances on the 
elements observed at places distributed over so large an area of the world. Thus, 
defects of observation and movements of the needle from magnetical causes could not 
be separated, and Rucker and Thorpe's method was reluctantly abandoned. 
With regard to the use of the Fox Dip and Intensity apparatus, it should be 
understood that, being a relative instrument, it was constantly compared with the 
absolute instruments. The index errors affecting the Dip observations were known 
to the nearest minute, and the change of magnetic force in the deflectors used in the 
force observations were ascertained by obtaining the values of the “weight equi¬ 
valents ” at four stations, so that the magnetic condition of the instrument was 
known whenever it was used. The temperature corrections were too small to be 
applied to force observations taken under conditions of small change of temperature. 
The results obtained on land with the absolute instruments are given in Table I. ; 
those with relative instruments in Table II. 
Local Magnetic Disturbances. 
Although the amount of local magnetic disturbance over given areas, and the 
causes thereof, have for some years past been a subject of close enquiry among 
magnetieians, it does not appear that anything like close attention has been paid to 
those local magnetic disturbances experienced on board ship which are independent of 
any direct action from iron or steel used in the construction of the ship. It is certain, 
however, that conclusions have been drawn and promulgated that are absolutely 
unfounded. Amongst them may be mentioned the erroneous impression that visible 
land, when miles distant, affects a ship’s compasses, to the danger of the ship. 
In view of placing the local magnetic disturbances observed in depths of water 
under 100 fathoms of water on a proper basis, instructions were given to H.M.S. 
“ Penguin ” to devote as much time to such an enquiry as her special surveying- 
duties would permit. H.M.S. “ Meda,” having reported on the remarkable disturb¬ 
ance of the compass experienced on board in the neighbourhood of Cossack, Port 
Walcott, in N.W. Australia, the results of a magnetic survey were of great import¬ 
ance to navigation, and consequently some days were devoted to the examination ol 
the port. A discussion of the observations made, with diagrams, forms the concluding 
and it is presumed the most important part of this paper. The results of observations 
made on islands and at Cossack for local magnetic disturbance will now be given in 
order of time. 
