100 REPORT—1862. 
many cases when a ship has been long sailing in one direction ; and this re- 
mark might be taken as a qualification of what we have remarked as to the 
permanence of the magnetism of a ship. 
On the fifth point we quite agree with the Liverpool Compass Com- 
mittee, subject, however, to the qualification that this correction cannot be 
depended on in the case of a newly-built ship, and that when the correction 
is applied to compasses having large deviations, and placed near large vertical 
masses of iron, as a stern-post, there must always be great uncertainty as to 
the correction on a change of magnetic latitude. It is also right that we 
should not pass over this remark without protesting against the application 
of such correction to the standard compass (properly placed) of a ship which 
may be called on to make a yoyage during which there is any great change in 
the dip or horizontal force. 
The Committee notice as the principal points left for further discussion 
and inquiry, the effect of heeling on the compasses of iron ships, and the 
changes which occur on a change of magnetic latitude ; and to these the 
Report is chiefly directed. 
On the effect of heeling a considerable body of evidence is collected, 
but with the disadvantage that at that time the mathematical theory of the 
heeling error, and the formule which express it, had not been fully investi- 
gated, and that consequently the comparison of theory with observation could 
not be precisely made; nor do the observations in all cases furnish sufficient 
data for the comparison. 
We think, however, that it may be said, with confidence, that the results 
of observations agree with theory as to the connexion between the amount 
and direction of the heeling error and the coefficients of quadrantal deviation 
and of horizontal and vertical force; and that we may therefore feel assured 
that the heeling error may be predicted with sufficient accuracy from obser- 
vations made on an even keel. 
The most important practical results as to the amount of the heeling 
error, are the very great amount to which it reaches in certain ships, and in 
gertain positions in the ship. This heeling error is conveniently measured 
by the fraction of a degree or the number of degrees of error produced by 
every degree of heel when the ship’s head is North or South. Estimating it 
in this way, it will be seen that the error may have serious effects if it exceed 
‘5 or -6, when an inclination of 10° may produce half a point of error. 
Among the examples given we have— 
Coefficients of 
Tron §. 8. City of Baltimore (built head North). heeling error, 
Compass placed above the aft end of iron round-house.. + 6°70 
Port steering-compass compensated ......-+ee ee eres — 30 
Starboard steering-compass compensated ........--.- — 50 
Diandard: Comsat is. oh Peed emis ip os ]e ied peter sans oben tury 4 +220 
Azimuth CONPPASS  «'s: shale Birla ole. dic'iijeistind 6 $6 cle wine +2: 
Dipping-needle compass ........ 4. seve sees eereenes +2: 
Fore compasscompensated ....... ccc ceereeecnceeee + °80 
Compass over fore hatch ......6c.ccer es onvinne caine + °85 
Aphrodite (built head East), 
Compass under companion ........ eee eeeee Sree. +2: 
Compass near COMPANION. ....... cs eevee este eens +285 
Admiralty standard compass .........4. SPIE LRG +1-20 
Dipping-needle compass vss sseevscreueeenreeeree +1:15 
