1866.] Mr. J. Lilley on the Action of Compasses in Iron Ships. 41 



place selected for the shore-compass. This is a matter of great importance, 

 far more than is often supposed. As the corrections made on hoard neces- 

 sarily depend upon the bearings given from the shore, if these are faulty, the 

 ship's compass cannot be otherwise than incorrect. 



The author has more than once seen a shore-compass within a very short 

 distance of an iron shed. The prevailing practice of swinging a ship in 

 the short space of two hours is also very objectionable ; it is utterly im- 

 possible to regulate compensating magnets, and to make the requisite ob- 

 servations for the use of soft iron, in so short a time ; it does not allow the 

 vessel to be stayed upon the several points for a sufficient scrutiny of the 

 compasses, sometimes three in number, and the results are too often merely 

 guessed at, and thus all the advantages of that admirable system of adjust- 

 ing iron vessels' compasses, introduced by the Astronomer Royal, and 

 which are invaluable to our coasting and short voyage vessels, are, to a 

 great extent, negatived. 



London is unfortunately very badly provided with the means of adjusting 

 the compasses of iron vessels, and, as their number is so much increasing, 

 this subject is daily becoming more important ; the docks are crowded, and 

 it is by mere chance that in the Victoria Dock, the only available dock at 

 our command, a sufficiently clear space is to be met with. Greenhithe 

 remains as the last resource in this dilemma ; here moorings have been laid 

 down by the City authorities for the use of merchant-vessels, but they are 

 too near the edge of the tide. A very strong down current exists ; the 

 entire space of slack water in the Reach is occupied by two sets of moorings 

 for the use of the Royal Navy. It would be a very great boon if one of 

 these sets of moorings were allowed to be used by the merchant service, 

 when not required for Her Majesty's Navy. It rarely happens that both 

 sets of moorings are at the same time required for use. As the swinging a 

 ship, moreover, at Greenhithe is entirely dependent upon the tide, it must 

 be commenced with the flood, added to which, the operation is often much 

 impeded by the wind, so that in the winter months, when the days are short, 

 and the seven hours of ebb occur during nearly the whole of daylight, 

 much serious delay is the result ; the author has often occupied three davs 

 in adjusting a ship's compasses. 



The construction of a dock for this purpose would be very desirable ; the 

 expense may be urged against the proposal ; but surely in London, one of 

 the greatest mercantile cities in Europe, such an undertaking should be 

 regarded as a national matter, and it is believed that shipowners would not 

 object to pay a small rate of charge for the use of such a dock which might 

 render it self-supporting. 



An opportunity for constructing such a dock may possibly arise in the 

 formation of the new docks at Dagenham, where the expense of an entrance 

 would be saved by simply making a basin from the dock large enough to 

 swing a ship 400 feet in length round a dolphin placed in the centre, and 

 well supplied with raooring-posts for ropes to be made fast to, and a suitable 



VOL. XV. E 



