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.
-----------+--------+-----+-----+----+---+-------------------------------NNeedlee---------------+---------------eMarked end aMarked end aAboveObs-dN. PoleS. Poletheer-l-------+-------+-------+------- StationDateSeaThermvereaa"a"a""
-----------+--------+-----+-----+----+---+-------+-------+-------+-------1831Feet.""""
PlymouthNov. 20{5058F.169 4969 06,569 5369 08{5058F.269 23,569 29,569 2669 25,51832Port PrayaJan. 28{2071F.146 46,546 1946 3645 40{2071F.246 16,546 23,546 2346 17{1683S.6 186 023 27,53 38 BahiaMar. 6 {1683S.7 19,57 021 391 54,5{1684S.7 599 29,51 08,51 54{1684S.6 296 02,54 11,54 11Rio de{1078S.13 4212 05,514 2714 05,5 JaneiroApr. 30{1078S.13 0211 54,515 15,515 16,5{1079S.14 2414 0612 04,513 03{Sept.5 {1849F.140 4542 5040 5043 42,5 Blanco Bay{{1849F.242 3441 47,541 1541 57 {Sept.19{1867F.141 2842 02,541 32,542 22 {{1867F.241 4841 5241 46,541 511833{Mar. 12{848F.153 2353 2756 2251 48 Falkland {{849F.253 2553 3250 4754 45 Islands {Mar.13 {850F.153 0853 5353 1953 59 {{851F.253 4053 3853 2753 34Monte VideoNov. 25{1084F.135 1034 4035 28,534 40{1084F.234 5534 47,534 2034 50{499} Port DesireDec. 30{4858F.153 0552 2953 2052 22,5{4858F.252 4552 27,552 4952 301834FalklandMar. 19{6045F.153 16,553 21,552 5854 05 Islands{6045F.253 4052 5853 2352 58{6045F.153 2352 4553 5953 08,5{6045F.253 1953 1953 2253 19River SantaMay 10 {2048F.155 3754 3755 4554 48 Cruz{2048F.255 3055 2155 2155 07Port SanDec. 24{862F.154 3254 1254 4054 00 Andres{862F.254 1954 1054 0753 491835Port LowJan. 15{657F.151 2750 4451 4251 00{657F.251 4851 4051 1051 10ChiloeJan. 26{1066F.149 1248 2949 3048 41{1066F.249 0949 0248 5748 51ValdiviaFeb. 18{869F.146 5846 1847 2246 34{869F.246 5646 4246 4446 38ConcepcionApr. 13{9059F.143 3042 4743 4742 58{9059F.243 2543 1543 1143 10ValparaisoJune 27{1557Sg.138 2437 2638 33,537 46{1557Sg.238 17,538 01,538 0037 56CallaoAug. 26{1264Sg.16 46,56 507 34,57 24{1264Sg.27 056 356 54,57 04,5GalapagosSept.22{672Sg.19 088 53,58 358 30 Islands{673Sg.28 29,58 40,58 42,58 31GalapagosOct. 16{870F.19 47,59 419 179 13,5 Islands{870F.29 24,59 32,59 269 27,5Otaheite, {Nov. 16{479Sg.130 0230 0630 39,529 51 or Tahiti {{479Sg.230 2129 5830 10,530 13 {Nov. 23{480Sg.130 17,530 1130 5830 05,5 {{480Sg.230 1830 07,530 0830 09 -----------+--------+-----+-----+----+---+-------+-------+-------+-------
{498} -----------+-------------------+------------------Place of StationDip deduced.Observation -----------+-------------------+------------------" "Plymouth69 29,1 } 69 27,6N.Athenaeum69 26,1 }Port Praya46 20,4 } 46 20,2N.Landing Place46 20,0 }4 51,5 }Bahia4 28,7 } 4 55,8N.San Antonio5 07,7 }(Dollond"s Instr.)5 13,5 }Rio de13 34,2 } 13 37,4S.Villegagnon Janeiro13 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 Video34 59,4 } 34 51,2S.Rat Island.
{499} Port Desire52 49,1 } 52 43,5S.Spanish Ruins.
52 37,9 }Falkland53 25,2 } 53 19,6S.Islands53 14,7 }Berkeley Sound,53 18,9 }Port Louis.
53 19,7 }River Santa55 11,7 } 55 15,7S.Keel Point.
Cruz55 19,7 }Port San54 21,0 } 54 13,6S.Christmas Andres54 06,2 }Cove.
Port Low51 13,2 } 51 20,1S.Observation51 27,0 }Islet.
Chiloe48 58 } 48 58,9S.San Carlos,48 59,8 }Pt. Arena.
Valdivia46 48 } 46 46,5S.Corral.
46 45 }Concepcion43 15,5 } 43 15,4S.Fort43 15,2 }Galvez.
Valparaiso38 02,4 } 38 03,1S.Near Fort38 03,8 }St. Antonio.
Callao7 08,7 } 7 02,8S.a.r.s.enal.
6 56,9 }Galapagos8 46,6 } 8 41,2N.Chatham Island, Islands8 35,9 }Stephen Bay.
Galapagos9 29,7 } 9 28,6N.Charles Islands9 27,6 }Island.
Otaheite, {30 09,6 } 30 13,5S.Point or Tahiti {30 10,6 }Venus.
{30 23 }{30 10,6 }-----------+-------------------+------------------
{500}
-----------+--------+-----+-----+----+---+-------------------------------NNeedlee---------------+---------------eMarked end aMarked end aAboveObs-dN. PoleS. Poletheer-l-------+-------+-------+------- StationDateSeaThermvereaa"a"a""
-----------+--------+-----+-----+----+---+-------+-------+-------+-------1835Feet.""""
New ZealandDec. 23{1063Sg.159 4459 04,560 09,559 14{1064Sg.259 43,559 28,559 32,559 19,51836SydneyJan. 15{2472Sg.163 00,562 26,563 1962 35{2472Sg.262 55,562 48,562 53,562 35,5Hobart TownFeb. 6 {3551Sg.170 51,570 1371 02,570 15,5{3551Sg.270 43,570 2770 3770 25,5King GeorgeMar. 8 {467Sg.164 57,564 17,565 0964 25 Sound{467Sg.264 49,564 3564 44,564 33KeelingApr. 4 {379Sg.138 48,537 45,539 0838 24 Islands{379Sg.238 43,538 3238 35,538 28MauritiusMay 3 {581Sg.154 21,553 2354 4153 46,5{581Sg.254 08,554 00,553 5853 47,5June 2{464Sg.152 5351 5353 14,552 22 Cape of{464Sg.252 40,552 32,552 3452 26 Good HopeJune 10{3565Sg.153 0352 3753 1452 27,5{3565Sg.252 3952 4052 3852 25St. HelenaJuly 11{1770Sg.118 0117 18,518 43,518 10,5{1770Sg.218 06,517 48,517 5518 05,5AscensionJuly 21{1572Sg.12 02,52 011 22,51 15,5 Island{1572Sg.21 25,51 521 48,51 26BahiaAug. 4 {674Sg.15 34,55 296 286 10,5{674Sg.26 015 48,55 356 01,6{501} PernambucoAug. 13{576F.113 3713 2413 0512 52{576F.213 1013 1513 1513 05{Sept. 1{1880Sg.146 19,545 22,545 5245 01 {{1880Sg.245 42,545 40,545 4745 36,5 Port Praya{Sept.2{2581Sg.146 49,545 53,546 07,545 16,5 {{2581Sg.246 0445 52,545 54,546 02,5 {Sept. 3{5080Sg.145 1545 2245 4845 08,5 {{5080Sg.245 42,545 3347 47,545 37TerceiraSept.21{472Sg.168 3967 4568 2467 45,5{472Sg.267 58,567 5968 1468 02,5FalmouthOct. 4{10058F.169 2969 2669 1669 19{10058F.269 1769 06,569 27,569 15,5PlymouthOct. 12{5054Sg.169 5468 59,569 46,568 40,5{5054Sg.269 15,569 0969 3369 10PlymouthOct. 15{10056Sg.169 5768 5469 16,568 43{10056Sg.269 1769 02,569 29,569 11 -----------+--------+-----+-----+----+---+-------+-------+-------+-------
{500} -----------+-------------------+------------------Place of StationDip deduced.Observation -----------+-------------------+------------------" "New Zealand59 33 } 59 32 S.Paihia Islet.
59 31 }Sydney62 50,2 } 62 49,4S.Fort Macquarie.
62 48,5 }Hobart Town70 35,6 } 70 34,9S.Fort Mulgrave.
70 34,2 }King George64 42,2 } 64 41,3S.Landing Place.
Sound64 40,5 }Keeling38 31,5 } 38 33,1S.Direction Inlet.
Islands38 34,7 }Mauritius54 03,1 } 54 00,8S.Cooper Island.
53 58,6 }52 35,6 } 52 34,4S.Simon Town.
Cape of52 33,2 }Good Hope52 35,4 } 52 35,5S.Observatory52 35,5 }(outside).
St. Helena18 03,4 } 18 01,2S.James Town.
17 59,0 }Ascension1 40,4 } 1 39,2N.Barrack Square.
Island1 38,0 }Bahia5 55,5 } 5 53,5N.San Antonio.
5 51,5 }{501} Pernambuco13 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 }Terceira68 08,4 } 68 06 N.Angra.
68 03,5 }Falmouth69 22,5 } 69 19,5Mr. Fox"s.
69 16,6 }Plymouth69 20,1 } 69 18,5N.Mount Wise.
69 16,9 }Plymouth69 20,1 } 69 17,6N.Athenaeum.
69 15 }-----------+-------------------+------------------
Observers:--F. Capt. FITZ-ROY. S. Lieut. SULIVAN. Sg. Mr. STEBBING