367 
LIEUT. CLERK’S REPORT: ELEMENTS OF REDUCTION. 
“ From the values of q tables of corrections were formed ; observing that when 
weights are used an increase of temperature gives an additive correction, and the 
contrary when the deflectors are used. As the values of q are small, and the greatest 
difference of temperature amounts only to 30°, the corrections are seldom of any im- 
portance ; they have however always been applied. 
“ f esides the observations made on board the Pagoda, others have been laid down 
on t e maps, in order to assist in drawing the magnetic lines. A series of observa- 
tions made by Lieut. Smith, R.N., between the Cape and Van Diemen Island, and 
another by Lieut. Dayman, R.N., between Van Diemen Island and the Cape (with the 
same instrument), have been laid down on the map of the Inclination. The same needles 
and deflectors were used in both cases. Lieut. Smith’s observations are all taken with 
the face of the instrument east; those of Lieut. Dayman’s with it both east and 
west. The following observations, made at the Ross Rank Observatory, Van Diemen 
Island, will serve to obtain the index corrections ; the inclination by the observatory 
needles being — /0° 40'. 
Observer. 
Direct. 
Def. N. 
Def. S. 
Def. N and S. 
Mean. 
Index cor- 
rection. 
Face of 
instrument. 
Lieut. Smith. 
Lieut. Dayman. 
Lieut. Smith. 
Lieut. Dayman. 
-71 39 
-71 40 
— 70 54 
-70 06 
O / 
-71 25 
— 71 22 
— 69 54 
-70 09 
o / 
-71 19 
—71 14 
-70 42 
— 70 13 
—71 36 | 
O / 
—71 28 
— 70 20 
/ 
+ 48 
-27 
East 
West 
r:::::: 
/ 
“ These colTect ions have been applied to all the observations made by Lieut. Smith ». 
“ As 110 observations were made for local attraction, we can only obtain approxi- 
mate corrections, by comparing observations made on or near the same spot with the 
ship’s head on different points of the compass. In the series made by Lieut. Smith 
we have the following observations : — 
August 14. 
August 18. 
September 10. 
September 13. 
E - i s _68 09 
E 67 28 
1 ° ' 
S W. -A fi. *7 O A 1 
O / 
s.E. by e. i e ... -68 06 
s-s.e —68 02 
E - by s -67 32 
e.s.e 67 38 
N - N - w —73 03 n.n.e —72 09 
From these comparisons it would appear that the correction is very small, espe- 
cially on the easterly points which were those generally observed upon ; the observa- 
tions have therefore been entered without any correction for the effect of the ship’s 
With regard to those of Lieut. Dayman, there are two cases where observations 
have been taken on different days, but in nearly the same position, and with the 
* When observations have been made with the face both east and west, the correction becomes + 10' • when 
weights as well as deflectors are used for the inclination, the correction face east and west becomes -13' ; this 
has been applied to the observations made by Lieut. Dayman. 
3 b 2 
