256 APPENDIX. 



for so marking the most eligible of these openings, that 

 they may be recognised in due lime, and passed through 

 in comparative safety ; and having thought fit to entrust 

 you with the command of an expedition to effect these 

 objects, we hereby require and direct you to take her 

 Majesty's cutter Bramble under your orders, and when she 

 and her Majesty's ship Fly, under your immediate com- 

 mand, shall be in every respect ready for sea, to proceed to 

 the island of Madeira, to verify the rates of your Chrono- 

 meters there, for which one day's observations will probably 

 suffice ; then to Simon's Bay, at the Cape of Good Hope, 

 to complete your water ; from thence to Van Diemen 

 Land, where you will compare the observations made with 

 your magnetic instruments with those made at the magnetic 

 observatory by Lieutenant Kay ; and then losing no further 

 time, you are to repair to Sydney. 



Having refitted your vessels, recruited your provisions, 

 and refreshed your crews, and having procured all the 

 information respecting the Barrier Reefs and openings that 

 can be obtained there, you will proceed to carry into exe- 

 cution the following objects ; and notwithstanding the order 

 in which they are here placed, we leave the several periods 

 of their performance to your own discretion. 



1. The survey of the exterior or eastern edge of that 

 vast chain of reefs which extends almost continuously from 

 Breaksea Spit to the shore of New Guinea. 



2. The thorough examination of all the channels through 

 the Barrier chain, with detailed plans of those which offer 

 a secure passage. 



3. When you have examined them all, and considered 

 their several advantages and difficulties, and determined 

 which of them will offer the speediest and safest passage for 

 the generality of merchant vessels, you will endeavour to 

 devise some practical means of marking them by beacons 



