ON AN IRON STEAM-VESSEL. 
285 
of that about the bows representing the marked end of a magnet, (or that which 
would point to the north,) and that about the stern the unmarked end, (or that 
which would point to the south,) the effects on the different needles being precisely 
similar to those which would have occurred had a magnet been placed in the position 
of the vessel. 
As both the bower-anchors were at the bows when the Garryowen approached the 
quay, magnetic effects may have been produced by their shanks and iron stocks ; but 
at the distance of 189 feet and 169 feet, where the instruments clearly developed 
their respective deflections, (see Tables VIII. and IX.) the result must, in my opinion, 
be attributed to the combined magnetic effect of the iron in those parts of the vessel 
which were nearest to the instruments. 
From the nature of the results I obtained on board the Garryowen, it would be 
advisable, as opportunities occur, to ascertain if similar effects are produced on the 
magnetic needle by other iron vessels, especially as respects the polarity of their 
heads and sterns, both before they have been put in motion through the water, and 
afterwards : this too might lead to other observations relative to the little oxidation 
that is reported to have taken place in the iron steam-vessel on the coast of Africa. 
As in the construction of iron vessels, hammering the numerous rivets might elicit 
magnetic influences, it would be well to note, by compass, the direction of their heads 
and sterns when building, with a view of ascertaining whether (in combination with 
the former circumstance) any distinct magnetic properties indicated by those parts 
are due to the line of direction of the vessel with respect to the magnetic meridian. 
The head of the Garryowen, when building, was west-north-west. 
§ 5. General Conclusions deduced from the experiments already made , with Notes on 
those which are requisite to be tried. 
The general conclusions relating to practical purposes that may be deduced from 
the experiments already tried are : 
1st, That the ordinary place for a steering-compass on board ship is an improper 
position for it on board an iron steam-vessel. 
2nd, That the binnacle-compass, in its usual place on board the Garryowen, is so 
much in error as not to be depended upon. 
3rd, That in selecting a position for a steering-compass on board iron steam-vessels, 
it is requisite that it should be placed, as far as may be practicable, not only above 
the general mass of iron but also above any smaller portions of iron in its vicinity, 
or that such portions should be removed -f~. 
* The great funnel is not alluded to here ; but should that prove to be an impediment, copper might easily 
be substituted. 
f The boat’s davits, iron stanchions, and rails about the quarter-deck are particularly alluded to, it being 
easy to substitute wood for the former and copper for the latter. 
