4 



HYDROGRAPHY. 



Telescopes for observing coincidences, &c., &c. Jones. 

 Two weekly chronometers, Nos. 1567 and 1503. Charles Frod- 

 sham. 



One Siderial chronometer, No. 1615. Charles Frodsham. 



Twenty-five 56hrs. Chronometers, viz. :— Nos. 2075, 2085, 2203, 

 1839, 2204, 2066, 2093, 2095, 1964, 2105, 2052, 2083, 2096, 2037, 

 by Parkinson and Frodsham; Nos. 2088, 3001, 1826, 2067, 2042, 2057, 

 by Molyneux; Nos. 972, 766, by Arnold and Dent ; Nos. 169, 170, by 

 Chas. Young; No. 850, by James Murray; and four Pocket chrono- 

 meters, viz. : Nos. 2124, 733, by Parkinson and Frodsham; No. 22, by 

 Molyneux, and No. 786, by Cotterel and Co. 



We were likewise provided with suitable libraries for each of the 

 larger vessels, and duplicate instruments of those which were liable 

 to be broken or become injured. For the repairs, there was attached 

 to the Expedition a competent instrument maker. Besides those 

 above enumerated, each officer was required to furnish himself with 

 a sextant, watch, &c. It will thus be seen that we were well pro- 

 vided for the performance of our duties. There were some instru- 

 ments I regretted not being able to procure, and among them was 

 Fox's magnetic dipping apparatus. 



Convenient portable houses and tents, for the protection and use 

 of the instruments, were also provided, which rendered us entirely 

 independent of external circumstance or local aid, so much so, that if 

 we had been obliged to occupy a bare sandbank, we should have 

 wanted for nothing ; and I trust that the labors performed will 

 exhibit abundant proof that the opportunities enjoyed were improved 

 with the utmost industry and all the energy we possessed. 



The reliance to be placed on Hydrographical labors depends upon 

 the accuracy of the modes employed in obtaining the results. It 

 therefore seems necessary to give a statement of these, and to explain 

 the combinations by which the positions that have been astronomically 

 determined are brought to prove and bear upon each other, thereby 

 affording strong evidence of the credit the combined results are entitled 

 to, and the confidence that ought to be placed in the surveys and charts 

 resulting from our labors. 



