Narrative of the surveying voyages of His Majesty's ships Adventure and Beagle Part 43

Cape Froward (Land behind the Morro) 2500 Est.

Cape Holland 1800 Est.

Mount Pond 2500 Est.

Mount Cross, Port Gallant { 2290 Bar.

{ 2264 Ang. 3 Obs.

Average height of the land near Sea Reach 1000 to 2500 Est.

OUTER COAST OF TIERRA DEL FUEGO.

Kater Peak, on Hermite Island 1742 Bar. 4 Obs.

Bell Mount, near Strait le Maire 4000 Est.[210]

Noir Island 600 Est.

SOUTH PACIFIC OCEAN.

WESTERN COAST OF PATAGONIA.

Mount Burney 4800 Ang.

Cape Three Points 2000 Est.

Mountain within Kelly Sound 1540 Ang.

Sugar Loaf (Marine Islands, in Holloway Sound) 1836 Ang.

Dome of St. Paul ( do. do. ) 2284 Ang.

Highest peak of Juan Fernandez (The Yungue, or Anvil) 3005 Ang.

{497}

MAGNETIC OBSERVATIONS,

DISCUSSED BY

MAJOR SABINE, R.A., F.R.S.

1. _Observations of the Dip._

Captain Fitz-Roy was furnished with two Dip Circles, one by Gambey, and the other by Dollond; the latter supplied by Government, and Gambey's purchased by himself.

Gambey's, being found to give results more accordant with each other than Dollond's, was used at all the stations, except Rio de Janeiro. The Circle was nine and a-half inches in diameter, and was furnished with two needles.

This instrument was, in all respects, a very superior one. It was placed for observation on a stand, which raised it from two to three feet above the ground. The needle was observed in eight positions, and as the readings accorded sufficiently well with each other, their arithmetical mean has been taken as the dip resulting from the observation. The eight positions were as follows: 1, with the graduated face of the circle towards the east; 2, with the same towards the west. The needle was then taken out and replaced with the ends of the axle changed, so that each end rested on a different plane to what it did before; it was then observed, 3, with the face of the circle towards the west, and 4, with the same to the east. The poles were then inverted, so that the end of the needle which was before a north pole became a south pole, and the four positions were again repeated.

The arc indicated by both ends of the needle was read in every position: an observation of the dip consisted, consequently, of sixteen readings. In the subjoined tabular record these are comprised in four entries, a mean being taken of the arc read at the two extremities of the needle, and of the positions 1 and 3, 2 and 4: 1 and 3 form the column, a; 2 and 4 the column, a'; and the same positions, with the poles reversed, the columns a" and a"'.

{498}

MAGNETIC DIP.

-----------+--------+-----+-----+----+---+------------------------------- N Needle e ---------------+--------------- e Marked end a Marked end a Above Obs- d N. Pole S. Pole the er- l -------+-------+-------+------- Station Date Sea Therm ver e a a' a" a"'

-----------+--------+-----+-----+----+---+-------+-------+-------+------- 1831 Feet. ' ' ' '

Plymouth Nov. 20{ 50 58 F. 1 69 49 69 06,5 69 53 69 08 { 50 58 F. 2 69 23,5 69 29,5 69 26 69 25,5 1832 Port Praya Jan. 28{ 20 71 F. 1 46 46,5 46 19 46 36 45 40 { 20 71 F. 2 46 16,5 46 23,5 46 23 46 17 { 16 83 S. 6 18 6 02 3 27,5 3 38 Bahia Mar. 6 { 16 83 S. 7 19,5 7 02 1 39 1 54,5 { 16 84 S. 7 59 9 29,5 1 08,5 1 54 { 16 84 S. 6 29 6 02,5 4 11,5 4 11 Rio de { 10 78 S. 13 42 12 05,5 14 27 14 05,5 Janeiro Apr. 30{ 10 78 S. 13 02 11 54,5 15 15,5 15 16,5 { 10 79 S. 14 24 14 06 12 04,5 13 03 { Sept.5 { 18 49 F. 1 40 45 42 50 40 50 43 42,5 Blanco Bay{ { 18 49 F. 2 42 34 41 47,5 41 15 41 57 { Sept.19{ 18 67 F. 1 41 28 42 02,5 41 32,5 42 22 { { 18 67 F. 2 41 48 41 52 41 46,5 41 51 1833 { Mar. 12{ 8 48 F. 1 53 23 53 27 56 22 51 48 Falkland { { 8 49 F. 2 53 25 53 32 50 47 54 45 Islands { Mar.13 { 8 50 F. 1 53 08 53 53 53 19 53 59 { { 8 51 F. 2 53 40 53 38 53 27 53 34 Monte Video Nov. 25{ 10 84 F. 1 35 10 34 40 35 28,5 34 40 { 10 84 F. 2 34 55 34 47,5 34 20 34 50 {499} Port Desire Dec. 30{ 48 58 F. 1 53 05 52 29 53 20 52 22,5 { 48 58 F. 2 52 45 52 27,5 52 49 52 30 1834 Falkland Mar. 19{ 60 45 F. 1 53 16,5 53 21,5 52 58 54 05 Islands { 60 45 F. 2 53 40 52 58 53 23 52 58 { 60 45 F. 1 53 23 52 45 53 59 53 08,5 { 60 45 F. 2 53 19 53 19 53 22 53 19 River Santa May 10 { 20 48 F. 1 55 37 54 37 55 45 54 48 Cruz { 20 48 F. 2 55 30 55 21 55 21 55 07 Port San Dec. 24{ 8 62 F. 1 54 32 54 12 54 40 54 00 Andres { 8 62 F. 2 54 19 54 10 54 07 53 49 1835 Port Low Jan. 15{ 6 57 F. 1 51 27 50 44 51 42 51 00 { 6 57 F. 2 51 48 51 40 51 10 51 10 Chiloe Jan. 26{ 10 66 F. 1 49 12 48 29 49 30 48 41 { 10 66 F. 2 49 09 49 02 48 57 48 51 Valdivia Feb. 18{ 8 69 F. 1 46 58 46 18 47 22 46 34 { 8 69 F. 2 46 56 46 42 46 44 46 38 Concepcion Apr. 13{ 90 59 F. 1 43 30 42 47 43 47 42 58 { 90 59 F. 2 43 25 43 15 43 11 43 10 Valparaiso June 27{ 15 57 Sg. 1 38 24 37 26 38 33,5 37 46 { 15 57 Sg. 2 38 17,5 38 01,5 38 00 37 56 Callao Aug. 26{ 12 64 Sg. 1 6 46,5 6 50 7 34,5 7 24 { 12 64 Sg. 2 7 05 6 35 6 54,5 7 04,5 Galapagos Sept.22{ 6 72 Sg. 1 9 08 8 53,5 8 35 8 30 Islands { 6 73 Sg. 2 8 29,5 8 40,5 8 42,5 8 31 Galapagos Oct. 16{ 8 70 F. 1 9 47,5 9 41 9 17 9 13,5 Islands { 8 70 F. 2 9 24,5 9 32,5 9 26 9 27,5 Otaheite, { Nov. 16{ 4 79 Sg. 1 30 02 30 06 30 39,5 29 51 or Tahiti { { 4 79 Sg. 2 30 21 29 58 30 10,5 30 13 { Nov. 23{ 4 80 Sg. 1 30 17,5 30 11 30 58 30 05,5 { { 4 80 Sg. 2 30 18 30 07,5 30 08 30 09 -----------+--------+-----+-----+----+---+-------+-------+-------+-------

{498} -----------+-------------------+------------------ Place of Station Dip deduced. Observation -----------+-------------------+------------------ ' ' Plymouth 69 29,1 } 69 27,6N. Athenaeum 69 26,1 } Port Praya 46 20,4 } 46 20,2N. Landing Place 46 20,0 } 4 51,5 } Bahia 4 28,7 } 4 55,8N. San Antonio 5 07,7 } (Dollond's Instr.) 5 13,5 } Rio de 13 34,2 } 13 37,4S. Villegagnon Janeiro 13 52,7 ) Island.

13 24,5) (Dollond's Instr.) { 42 01,9 } Blanco Bay{ 41 53,4 } 41 54 S. The Wells at { 41 51,2 } Point Johnson.

{ 41 49,4 } { 53 45 } Falkland { 53 07,2 } 53 30,4S. Berkeley Sound, Islands { 53 34,7 } Magellan or { 53 34,8 } Johnson Cove.

Monte Video 34 59,4 } 34 51,2S. Rat Island.

{499} Port Desire 52 49,1 } 52 43,5S. Spanish Ruins.

52 37,9 } Falkland 53 25,2 } 53 19,6S. Islands 53 14,7 } Berkeley Sound, 53 18,9 } Port Louis.

53 19,7 } River Santa 55 11,7 } 55 15,7S. Keel Point.

Cruz 55 19,7 } Port San 54 21,0 } 54 13,6S. Christmas Andres 54 06,2 } Cove.

Port Low 51 13,2 } 51 20,1S. Observation 51 27,0 } Islet.

Chiloe 48 58 } 48 58,9S. San Carlos, 48 59,8 } Pt. Arena.

Valdivia 46 48 } 46 46,5S. Corral.

46 45 } Concepcion 43 15,5 } 43 15,4S. Fort 43 15,2 } Galvez.

Valparaiso 38 02,4 } 38 03,1S. Near Fort 38 03,8 } St. Antonio.

Callao 7 08,7 } 7 02,8S. a.r.s.enal.

6 56,9 } Galapagos 8 46,6 } 8 41,2N. Chatham Island, Islands 8 35,9 } Stephen Bay.

Galapagos 9 29,7 } 9 28,6N. Charles Islands 9 27,6 } Island.

Otaheite, { 30 09,6 } 30 13,5S. Point or Tahiti { 30 10,6 } Venus.

{ 30 23 } { 30 10,6 } -----------+-------------------+------------------

{500}

-----------+--------+-----+-----+----+---+------------------------------- N Needle e ---------------+--------------- e Marked end a Marked end a Above Obs- d N. Pole S. Pole the er- l -------+-------+-------+------- Station Date Sea Therm ver e a a' a" a"'

-----------+--------+-----+-----+----+---+-------+-------+-------+------- 1835 Feet. ' ' ' '

New Zealand Dec. 23{ 10 63 Sg. 1 59 44 59 04,5 60 09,5 59 14 { 10 64 Sg. 2 59 43,5 59 28,5 59 32,5 59 19,5 1836 Sydney Jan. 15{ 24 72 Sg. 1 63 00,5 62 26,5 63 19 62 35 { 24 72 Sg. 2 62 55,5 62 48,5 62 53,5 62 35,5 Hobart Town Feb. 6 { 35 51 Sg. 1 70 51,5 70 13 71 02,5 70 15,5 { 35 51 Sg. 2 70 43,5 70 27 70 37 70 25,5 King George Mar. 8 { 4 67 Sg. 1 64 57,5 64 17,5 65 09 64 25 Sound { 4 67 Sg. 2 64 49,5 64 35 64 44,5 64 33 Keeling Apr. 4 { 3 79 Sg. 1 38 48,5 37 45,5 39 08 38 24 Islands { 3 79 Sg. 2 38 43,5 38 32 38 35,5 38 28 Mauritius May 3 { 5 81 Sg. 1 54 21,5 53 23 54 41 53 46,5 { 5 81 Sg. 2 54 08,5 54 00,5 53 58 53 47,5 June 2{ 4 64 Sg. 1 52 53 51 53 53 14,5 52 22 Cape of { 4 64 Sg. 2 52 40,5 52 32,5 52 34 52 26 Good Hope June 10{ 35 65 Sg. 1 53 03 52 37 53 14 52 27,5 { 35 65 Sg. 2 52 39 52 40 52 38 52 25 St. Helena July 11{ 17 70 Sg. 1 18 01 17 18,5 18 43,5 18 10,5 { 17 70 Sg. 2 18 06,5 17 48,5 17 55 18 05,5 Ascension July 21{ 15 72 Sg. 1 2 02,5 2 01 1 22,5 1 15,5 Island { 15 72 Sg. 2 1 25,5 1 52 1 48,5 1 26 Bahia Aug. 4 { 6 74 Sg. 1 5 34,5 5 29 6 28 6 10,5 { 6 74 Sg. 2 6 01 5 48,5 5 35 6 01,6 {501} Pernambuco Aug. 13{ 5 76 F. 1 13 37 13 24 13 05 12 52 { 5 76 F. 2 13 10 13 15 13 15 13 05 { Sept. 1{ 18 80 Sg. 1 46 19,5 45 22,5 45 52 45 01 { { 18 80 Sg. 2 45 42,5 45 40,5 45 47 45 36,5 Port Praya{ Sept.2{ 25 81 Sg. 1 46 49,5 45 53,5 46 07,5 45 16,5 { { 25 81 Sg. 2 46 04 45 52,5 45 54,5 46 02,5 { Sept. 3{ 50 80 Sg. 1 45 15 45 22 45 48 45 08,5 { { 50 80 Sg. 2 45 42,5 45 33 47 47,5 45 37 Terceira Sept.21{ 4 72 Sg. 1 68 39 67 45 68 24 67 45,5 { 4 72 Sg. 2 67 58,5 67 59 68 14 68 02,5 Falmouth Oct. 4{ 100 58 F. 1 69 29 69 26 69 16 69 19 { 100 58 F. 2 69 17 69 06,5 69 27,5 69 15,5 Plymouth Oct. 12{ 50 54 Sg. 1 69 54 68 59,5 69 46,5 68 40,5 { 50 54 Sg. 2 69 15,5 69 09 69 33 69 10 Plymouth Oct. 15{ 100 56 Sg. 1 69 57 68 54 69 16,5 68 43 { 100 56 Sg. 2 69 17 69 02,5 69 29,5 69 11 -----------+--------+-----+-----+----+---+-------+-------+-------+-------

{500} -----------+-------------------+------------------ Place of Station Dip deduced. Observation -----------+-------------------+------------------ ' ' New Zealand 59 33 } 59 32 S. Paihia Islet.

59 31 } Sydney 62 50,2 } 62 49,4S. Fort Macquarie.

62 48,5 } Hobart Town 70 35,6 } 70 34,9S. Fort Mulgrave.

70 34,2 } King George 64 42,2 } 64 41,3S. Landing Place.

Sound 64 40,5 } Keeling 38 31,5 } 38 33,1S. Direction Inlet.

Islands 38 34,7 } Mauritius 54 03,1 } 54 00,8S. Cooper Island.

53 58,6 } 52 35,6 } 52 34,4S. Simon Town.

Cape of 52 33,2 } Good Hope 52 35,4 } 52 35,5S. Observatory 52 35,5 } (outside).

St. Helena 18 03,4 } 18 01,2S. James Town.

17 59,0 } Ascension 1 40,4 } 1 39,2N. Barrack Square.

Island 1 38,0 } Bahia 5 55,5 } 5 53,5N. San Antonio.

5 51,5 } {501} Pernambuco 13 14,5 } 13 12,9N. a.r.s.enal.

13 11,5 } { 45 38,9 } { 45 41,6 } Landing Place.

Port Praya{ 46 01,7 } 45 46,5N. { 45 58,6 } { 45 38,4 } Quail Island.

{ 45 40,0 } Terceira 68 08,4 } 68 06 N. Angra.

68 03,5 } Falmouth 69 22,5 } 69 19,5 Mr. Fox's.

69 16,6 } Plymouth 69 20,1 } 69 18,5N. Mount Wise.

69 16,9 } Plymouth 69 20,1 } 69 17,6N. Athenaeum.

69 15 } -----------+-------------------+------------------

Observers:--F. Capt. FITZ-ROY. S. Lieut. SULIVAN. Sg. Mr. STEBBING