CORRECTING OF SHIPS' COMPASSES.

New Zealand Herald, Volume XXIV, Issue 7914, 5 April 1887, Page 6

CORRECTING OF SHIPS' COMPASSES.

TO THE EDITOR. Sin, —In your issue of the 31st ulfc., I noticed a paragraph in relation to wooden vessels when laden with oil in tins having their compasses affected in a remarkable way. This would also occur in iron-built ships, from the simple fact that the vessels which are called tin, euch as those used for canning meat, fruits, oil, and a thousand and one other articles, so to speak, are made of iron, tinned over. A moment's reflection will show thst the price of tin would make it far too costly a material to be used for the above purposes. If a magnet be applied to any of these articles the attraction will at once be perceived, hence the reason of the compasses being so disturbed becomes obvious. This being ao I may venture to remark on the necessity of not only knowing that the compasses are in error, but being able to ascertain the amount on each point. All vessels should be furnished .with the means of determining this. It may perhaps not be known to all that at the cost of a few shillings such, a desideratum may be obtained as will enable the master, with a little calculation, taking very little time, to ascertain the deviation of his compass' on any course. When a ship ie swung for adjustment, strictly speaking the results are only correct under the conditions then existing, as during the intervals of the authorised periodical swingings she may change her position geographically, even to a different hemisphere—may also have a variety of cargo, constating more or less of railway iron, machinery, etc. Four wooden ships that I know of were in danger on account of errors, etc., in their compasses. Two of these vessels were afterwards lost. If you can bring your influence to bear on this important matter, you will confer a benefit on all who are in any way interested in shipping,, as you have already done in introducing thli subject.—l arn, etc., Marinkb. ' Auckland, April 2, ISS7.