280 
COMMANDER JOHNSON’S MAGNETIC EXPERIMENTS 
of His Majesty’s ships. These positions were G* * * § , P, C-f-, and, by the last series of 
observations, I, may be added : the three former, however, were inconvenient situa- 
tions, and it therefore became necessary to try the latter (I) more particularly, by 
observing the dip and intensity as well as the horizontal deflections, with a view to 
ascertain how near a compass might be approached towards the deck with propriety, 
for the discrepancies observed at D, I attribute to the proximity of the boats’ davits. 
It will be proper to notice in this place some particulars which bear upon the 
question as relates to three parts of the vessel, viz. forward, amidships, and abaft ; it 
being here understood that the place spoken of for the compass is above the mass of 
iron in these parts. 
1 st. Forward. — The forecastle regarded as a position for a compass is not favour- 
able in a practical point of view;}:, as it would be in the way of a variety of work; and 
in small vessels, during gales of wind, as the men cannot always keep their stations 
there, it would be insecure. 
The anchors, chain-cables, &c. being in the immediate vicinity, would be disadvan- 
tageous as relates to the local attraction, and with respect to motion (and in an iron 
vessel magnetism) it is not a favourable position §. 
2nd, Amidships . — The centre, or rather immediately above the centre as respects 
length and breadth, would be a desirable place as to motion, and probably as to mag- 
netism, if the large funnel were made of copper instead of iron ; that is, if we may 
consider the vessel as an entire magnet ; but against these premises is one of con- 
siderable consequence, viz. that the connecting-rods, shafts, cross-heads, &c. of the 
machinery are moveable quantities, and therefore it would be improper to place the 
compass within the range of their influence. 
Between the foremast and the great funnel, the crane, being made of iron, and also 
the crank and cylinder-hatches, renders such a position unfavourable. 
3rd, Abaft . — From the position of the great funnel, and the disposition of a variety 
of smaller portions of iron above the deck of the Garryowen, the quarter-deck (and 
of course above the mass of iron) appears to me to be the most eligible position for a 
steering-compass. 
* Previously to the compass G being placed on the cross-plank (which was supported by two wooden lad- 
ders) the chain peak halyards were unrove, and rope was substituted ; and after the first revolution of the 
vessel two small blocks on the gaff having been discovered to have iron pins, they were removed, so that the 
small bolt for the peak downliaul only remained, and this was 4 feet above the compass. 
t After the first series of observations with compass C (which was mounted on glass legs) the large hoop of 
iron which was on the outer end of the bowsprit, about 4 feet from the compass, was removed, but the iron 
pin for the sheave block, which was nearly the same distance, still remained, as it was found inconvenient to 
displace. 
X I am aware that it has been suggested to steer steam-vessels on the forecastle, by leading their tiller-ropes 
forward ; but the above remarks have reference only to placing the compass. 
§ These remarks do not apply to the bowsprit, as the results at C are so curious as to require further expe- 
riments, especially when contrasted with those over the stem. 
