Narrative of the surveying voyages of His Majesty's ships Adventure and Beagle, between the years 1826 and 1836. Volume I. Proceedings of the First Expedition, 1826-1830

by Robert Fitzroy; Philip Parker King

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″′.

Magnetic Dip.

Station.	Date.	Above the Sea.	Therm.	Obs- erver.	Needle.	Needle				Dip Deduced.	Place of Observation.
						Marked end a N. Pole.		Marked end a S. Pole.
						a	a′	a″	a″′
	1831	Feet.	°			° ′	° ′	° ′	° ′	° ′ ° ′
Plymouth	Nov. 20	50	58	F.	1	69 49	69 06,5	69 53	69 08	69 29,1 69 27,6N. 69 26,1	Athenæum
		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	46 20,4 46 20,2N. 46 20,0	Landing Place
		20	71	F.	2	46 16,5	46 23,5	46 23	46 17
Bahia	Mar. 6	16	83	S.		6 18	6 02	3 27,5	3 38	4 51,5 4 55,8N. 4 28,7 5 07,7 5 13,5	San Antonio (Dollond's Instr.)
		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 Janeiro	Apr. 30	10	78	S.		13 42	12 05,5	14 27	14 05,5	13 34,2 13 37,4S. 13 52,7 13 24,5	Villegagnon Island. (Dollond's Instr.)
		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
Blanco Bay	Sept.5	18	49	F.	1	40 45	42 50	40 50	43 42,5	42 01,9 41 54 S. 41 53,4 41 51,2 41 49,4	The Wells at Point Johnson.
		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
Falkland Islands	Mar. 12	8	48	F.	1	53 23	53 27	56 22	51 48	53 45 53 30,4S. 53 07,2 53 34,7 53 34,8	Berkeley Sound, Magellan or Johnson Cove.
		8	49	F.	2	53 25	53 32	50 47	54 45
	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	34 59,4 34 51,2S. 34 43,1	Rat Island.
		10	84	F.	2	34 55	34 47,5	34 20	34 50
Port Desire	Dec. 30	48	58	F.	1	53 05	52 29	53 20	52 22,5	52 49,1 52 43,5S. 52 37,9	Spanish Ruins.
		48	58	F.	2	52 45	52 27,5	52 49	52 30
	1834
Falkland Islands	Mar. 19	60	45	F.	1	53 16,5	53 21,5	52 58	54 05	53 25,2 53 19,6S. 53 14,7 53 18,9 53 19,7	Berkeley Sound, Port Louis.
		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 Cruz	May 10	20	48	F.	1	55 37	54 37	55 45	54 48	55 11,7 55 15,7S. 55 19,7	Keel Point
		20	48	F.	2	55 30	55 21	55 21	55 07
Port San Andres	Dec. 24	8	62	F.	1	54 32	54 12	54 40	54 00	54 21,0 54 13,6S. 54 06,2	Christmas Cove
		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	51 13,2 51 20,1S. 51 27,0	Observation Islet
		6	57	F.	2	51 48	51 40	51 10	51 10
Chilóe	Jan. 26	10	66	F.	1	49 12	48 29	49 30	48 41	48 58 48 58,9S. 48 59,8	San Carlos, Pt. Arena.
		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	46 48 46 46,5S. 46 45	Corral.
		8	69	F.	2	46 56	46 42	46 44	46 38
Concepçion	Apr. 13	90	59	F.	1	43 30	42 47	43 47	42 58	43 15,5 43 15,4S. 43 15,2	Fort Galvez.
		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	38 02,4 38 03,1S. 38 03,8	Near Fort St. Antonio.
		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	7 08,7 7 02,8S. 6 56,9	Arsenal.
		12	64	Sg.	2	7 05	6 35	6 54,5	7 04,5
Galapagos Islands	Sept.22	6	72	Sg.	1	9 08	8 53,5	8 35	8 30	8 46,6 8 41,2N. 8 35,9	Chatham Island, Stephen Bay
		6	73	Sg.	2	8 29,5	8 40,5	8 42,5	8 31
Galapagos Islands	Oct. 16	8	70	F.	1	9 47,5	9 41	9 17	9 13,5	9 29,7 9 28,6N. 9 27,6	Charles Island.
		8	70	F.	2	9 24,5	9 32,5	9 26	9 27,5
Otaheite, or Tahiti	Nov. 16	4	79	Sg.	1	30 02	30 06	30 39,5	29 51	30 09,6 30 13,5S. 30 10,6 30 23 30 10,6	Point Venus.
		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
New Zealand	Dec. 23	10	63	Sg.	1	59 44	59 04,5	60 09,5	59 14	59 33 59 32 S. 59 31	Paihia Islet.
		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	62 50,2 62 49,4S. 62 48,5	Fort Macquarie.
		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	70 35,6 70 34,9S. 70 34,2	Fort Mulgrave.
		35	51	Sg.	2	70 43,5	70 27	70 37	70 25,5
King George Sound	Mar. 8	4	67	Sg.	1	64 57,5	64 17,5	65 09	64 25	64 42,2 64 41,3S. 64 40,5	Landing Place.
		4	67	Sg.	2	64 49,5	64 35	64 44,5	64 33
Keeling Islands	Apr. 4	3	79	Sg.	1	38 48,5	37 45,5	39 08	38 24	38 31,5 38 33,1S. 38 34,7	Direction Inlet.
		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	54 03,1 54 00,8S. 53 58,6	Cooper Island.
		5	81	Sg.	2	54 08,5	54 00,5	53 58	53 47,5
Cape of Good Hope	June 2	4	64	Sg.	1	52 53	51 53	53 14,5	52 22	52 35,6 52 34,4S. 52 33,2	Simon Town.
		4	64	Sg.	2	52 40,5	52 32,5	52 34	52 26
	June 10	35	65	Sg.	1	53 03	52 37	53 14	52 27,5	52 35,4 52 35,5S. 52 35,5	Observatory (outside)
		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	18 03,4 18 01,2S. 17 59,0	James Town.
		17	70	Sg.	2	18 06,5	17 48,5	17 55	18 05,5
Ascension Island	July 21	15	72	Sg.	1	2 02,5	2 01	1 22,5	1 15,5	1 40,4 1 39,2N. 1 38,0	Barrack Square.
		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	5 55,5 5 53,5N. 5 51,5	San Antonio.
		6	74	Sg.	2	6 01	5 48,5	5 35	6 01,6
Pernambuco	Aug. 13	5	76	F.	1	13 37	13 24	13 05	12 52	13 14,5 13 12,9N. 13 11,5	Arsenal.
		5	76	F.	2	13 10	13 15	13 15	13 05
Port Praya	Sept. 1	18	80	Sg.	1	46 19,5	45 22,5	45 52	45 01	45 38,9 45 46,5N. 45 41,6 46 01,7 45 58,6 45 38,4 45 40,0	Landing Place.
		18	80	Sg.	2	45 42,5	45 40,5	45 47	45 36,5
	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		Quail Island.
		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	68 08,4 68 06 N. 68 03,5	Angra.
		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	69 22,5 69 19,5N. 69 16,6	Mr. Fox's.
		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	69 20,1 69 18,5N. 69 16,9	Mount Wise.
		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	69 20,1 69 17,6N. 69 15	Athenæum.
		100	56	Sg.	2	69 17	69 02,5	69 29,5	69 11

Observers:—F. Capt. Fitz-Roy.S. Lieut. Sulivan.Sg. Mr. Stebbing

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