1 85 1 .] On the Rates of Chronometers. 65 



I suggested that this might be owing to an increase in the ship's 

 local attraction if she had a larger proportion of iron in her cargo on the 

 present voyage, or her usual quantity differently placed 1 This he also 

 thought probable, and stated that he had had more Iron ou this 

 voyage, and moreover mentioned that the same variation of rate had 

 occurred on board of other ships which had brought out a large quan- 

 tity of iron. I thought this is a question of much interest both to 

 seamen and to hydrographical science, and I forthwith drew up a set of 

 queries on the subject, to which Captain Hopkins of the Prince of 

 Wales, Captain M c Leod of the Queen and Capt. Lay of the Tudor 

 have obliged me with replies. All these are large passenger ships ; the 

 Tudor brought out less iron on this voyage than usual and also found 

 her Chronometers in error, but the causes of this will be seen in the 

 reply to query No. 10. In a note to me Capt. Lay says, " I had more 

 difference than usual, and one Chronometer became quite useless which 

 has been my best going one for 1 3 years." I have printed these replies as 

 follows, distinguishing Captain Hopkin's replies by the letter H. Captain 

 M c Leod's by M C L. and those of Capt. Lay by L., and I have preferred to 

 give them with the queries, because they may be useful on a future 

 occasion, or suggest other enquiries or hints as the subject is more 

 developed ; for it is evidently one of high importance and of which we 

 have yet much knowledge to acquire, and which offers a wide field alike 

 for the careful observer of all classes and for the ingenuity of the 

 scientific workman in the construction of these invaluable instruments. 



Queries for ascertaining the cause of the alteration in the Rates of 

 Chronometers on board the ship — 



General. 



1. What was the whole error H. — Forty miles East of the 



of your Chronometers on the voy- true position of the Floating Light 



age taking the mean of the two Vessel. 



or three best of them and if + or M C L.— 53f miles East of Cal- 



— of the shore rate. State how cutta by mean of 3 Chronometers, 



many miles (of arc) you were East L. — The variation from true 



or West of the Light Vessel or rate was Oh. 2' 7-2". 32 miles, 

 other position ? 



