E. TOTAL INTENSITY. 
As we have already mentioned, deflection observations were frequently 
made in connection with the inclination determinations, for the determination 
of the total intensity. The alhidade on the back of the vertical circle with 
one or both deflectors screwed in, was set with its zero exactly at the division 
of the limb that indicated the mean of the inclination readings obtained 
immediately before, with the same position of the instrument, “Circle E” or 
“Circle W”. <A series of readings of both ends of the needle were then 
taken, first with the needle deflected within one quadrant, and next a cor- 
responding series with the needle deflected past the vertical. The thermo- 
meter belonging to the Fox apparatus proved several times to be out of 
order, and in these cases another thermometer was introduced into the box 
of the inclination-needle. 
Only in five cases were both the deflectors used together; on all other 
occasions only the one deflector marked N was employed. 
In analogy with the formula given on page 130, we obtain, as an 
expression for the total intensity W, 
(1) 
where #,, ¢, and w, are substituted for R,, ¢, and w., and indicate the 
corresponding quantities applicable in the case of only the one deflector 
being employed. No determination of the constants R, and €, were made 
either before the voyage, in Hamburg, or after the return, at Wilhelmshaven. 
