■^pfvi.
1
KA.GM'.niant IKOl
y ^ ^NEW AMERICAN
PRACTICAL NAVIGATOR:
EPITOME OF NAVIGATION;
CONTAINING ALL THE
TABLES
NECESSARY TO BE USED WITH THE NAUTICAL ALMANAC
IN
DETERMINING THE LATITUDE, AND THE LONGITUDE BY LUNAR OBSERVATIONS,
AND
KEEPING A COMPLETE RECKONING AT SEA;
ILLUSTRATED BY
PROPER RULES AND EXAMPLES:
THE WHOLE EXEMPLIFIED IN A JOURNAL,
KEPT FROM BOSTON TO MADEIRA, IN WHICH
ALL THE RULES QF NAVIGATION ARE INTRODUCED i
ALSO,
THE DEMONSTRATION OF THE USUAL RULES OF TRIGONOMETRY ; TROBLiftlS IB
MENSURATION, SURVEYING, AND GAUGING , DICTIONARY OF SEA TERMS ;
AND THE MANNER OF PERFORMING THE MOST USEFUL
EVOLUTIONS AT SEA :
WITH
AN APPENDIX,
CONTAINING
METHODS OF CALCULATING ECLIPSES OF THE SUN AND MOON, AND OCCULTATIONS OF THE
FIXED STARS ; RULES FOR FINDING THE LONGITUDE OF A PLACE BY OBSERVATIONS
OF ECLIPSES, OCCULTATIONS, AND TRANSITS OF THE MOON'S LIMB OVER
THE MERIDIAN ; ALSO A NEW METHOD FOR FINDING THE
LATITUDE BY TWO ALTITUDES.
BY NATHANIEL BOWDITCH, LL. D.
Fellow of the Royal Societies of London, Edinburgh, and Dublin; of the Astronomical Society in London: "j
(At American Philosophical Society, h eld at Philadelphia ; of the American Academy of Arts and
Sciences; of the Connecticut Academy of Arts and Sciences ; of the Literary and
Philosophical Society of JWm York ; Corresponding Member of the
Royal Societies of Berlin, Palermo, &-c., — and, since
his decease, continued by his son,
J. INGERSOLL BOWDITCH.
THIRTIETH NEW STEREOTYPE EDITION.
NEW-YORK: PUBLISHED BY E. & G. W. BLUNT, PROPRIETORS,
No. 179 WATER-STREET, CORNER OF BITRLING SLIP.
STEREOTYPED AT THE BOSTON TYPE AND STEREOTYPE FOUNDRY.
1861.
X . «NEW AMERICAN
PRACTICAI. NAVIGATOR:
BEING AN
EPITOME OF NAVIGATION;
CONTAINING ALL THE
TABLES
NECESSARY TO BE USED WITH THE NAUTICAL ALMANAC
IN
DETERMINING THE LATITUDE, AND THE LONGITUDE BY LUNAR OBSERVATIONS,
AND
KEEPING A COMPLETE RECKONING AT SEA;
ILLUSTRATED BY
PROPER RULES AND EXAMPLES:
THE WHOLE EXEMPLIFIED IN A JOURNAL,
KEPT FROM BOSTON TO MADEIRA, IN WHICH
ALL THE RULES OF NAVIGATION ARE INTRODUCED i
ALSO,
THE DEMONSTRATION OF THE USUAL RULES OF TRIGONOMETRT ; FROBLiMS IS
MENSURATION, SURVEYING, AND GAUGING , DICTIONARY OF SEA TERMS *.
AND THE MANNER OF PERFORMING THE MOST USEFUL
EVOLUTIONS AT SEA :
WITH
AN APPENDIX,
CONTAINING
METHODS OF CALCULATING ECLIPSES OF THE SUN AND MOON, AND OCCULTATIONS OF THE
FIXED stars; RULES FOR FINDING THE LONGITUDE OF A PLACE BY OBSERVATIONS
OF ECLIPSES, OCCULTATIONS, AND TRANSITS OF THE MOON'S LIMB OVER
THE MERIDIAN; ALSO A NEW METHOD FOR FINDING THE
LATITUDE BY TWO ALTITUDES.
BY NATHANIEL BOWDITCH, LL. D.
Fellow »f the Royal Societies of London, Edinburgh, and Dublin; of the Astronomical Society in London; of
the American Philosophical Society, held at Philadelphia ; of the Jimerican Academy of Arts and
Sciences; of the Connecticut Academy of Arts and Sciences; of the Literary and
Philosophical Society of J^Tew York; Corresponding Member of the
Royal Societies of Berlin, Palermo, &-c., — and, since
his decease, continued by his son,
J. INGERSOLL BOWDITCH.
THIRTIETH NEW STEREOTYPE EDITION.
NEW-YORK: PUBLISHED BY E. & G. W. BLUNT, PROPRIETORS,
No. 170 WATER-STREET, CORNER OF BURLING SLIP.
STEREOTYPED AT THE BOSTON TYPE AND STEREOTYPE FOUNDRY.
1861.
NOTICE TO THE 30th EDITION.
Some corre'ctrbn's in tlie Latitude and Longitude of points on the coast of Cuba iia^^e Ijee.n made. ' TLe Pole 'Star 'table, o: page 206, has been altered to correspond nearly to the year 1860.
Table LV. has been corrected from the " Tide Tables for the English and Irish Ports for 1860." From Mr. Portales I have received valuable aid.
The article on " Tides," on pages 120, &c., was prepared by Dr. Bache.
Captain Josiah Snow, of the ship Asterion, informs me, that the doubtful shoal in Macassar Straits, laid down in 4° 50' S. and 116° 50' E., is about three miles broad in the shoalest part, and bears N. W. by W. from the North Seras seven miles ; in some places there is not over six feet of water. By good observations he places it in 116° 58' E.
On Sahul Bank, off Timor, in lat. 10° 50' S. and 127° 40' E., he passed a shoal or reef a quarter of a mile long East and West ; some of the rocks were even with the water's edge. Captain Snow, in the lat. 10° 54^ S. and 127° 05' E., passed a line of breakers two miles long, running East and West, and from appearances thought there must be many shoal spots in the ' neighborhood. He thinks nearly all the islands East of Mindoro are laid down erroneous, and should not be depended upon — especially Semerara, the largest, which should be 12 miles further north.
From Mr. Daniel P. Upton, I learn that, in 1859, the Dutch bark "Hoop von Capello" struck on a sharp coral rock, about 20 feet long, in the Straits of Augier, having 16 feet of water on it. The compass bearings are —
The Cap N. W. by W. 4° W.
Point Tanjong Lemuing S. -j W.
4 Point Lio-ht S. W.
The " Caimsmore" Rock is a small, dangerous, and very abrupt rock, 30 or 40 feet in diameter, on which the ship Caimsmore was totally lost 26th June, 1858. Lat. 30° 42' 10" N. Long. 122° 34' 40" E.
The geographical position of some of the Shoals, Rocks, &c., in the " Coral Sea," have been corrected from the Surveys of 1859, and new positions added on p. 451.
I860. J. INGERSOLL BOWDITOH.
Entered according to Act of Congress, la the year of our Lord ISSY, by E. & G. W. Blunt, in the Clerk's Office of the District Court for the Southern District of K"ew York.
For new Nautical Publications, &c., of E. &. G. ^Y. Blunt, see adv'ertibiment at the end.
Printed by Joseph Russell, 79 John bx. IN MEMORrAM
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tPage 1.
CORRECTIONS AND ADDITIONS
TO GEOGRAPHICAL POSITIONS IN TABLE LIV. OF BOWDITCH S NAVIGATOR, EDITION OF 1851.
Kindly furnished by Dr. Bache, Superintendent of the U. S. Coast Survey, by authority of the Treasury Department,
J^AME OF PLACES.
Cape Elizabeth West Light Cape Elizabeth East Light ,
Wood Island Light
Agamenticus Hill
Plum Island East Light
Plum Island West Light
Beverley Spire
Ipswich East Light
Ipswich West Light
Squara Light
Straits mouth Island Light
Thatcher's Island South Light Thatcher's Island North Light
Ten pound Island Light
Eastern Point Light
Eaker's Island Light
Salem, Tall Spire
Marblehead, Black Top Church
Nahant Hotel
BOSTON, State-House
Cambridge Observatory Dome
Bunker Hill Monument
Scituate Light
Boston Light
Long Island Light
Plymouth Light
Race Point Light
Cape Cod Light
Long Point Light
WeUfleet Light
Billingsgate Point Light
Nausett Centre Light..
Nausett South Liglit
Chatham South Light
ilouomoy Light ,
New Bedford Light
Cape Pogue Light
Great Point Light
Brant Point Beacon
Saukaty Head Light
Nantucket Harbor Light
Nantucket Old South Shoal .... Nantucket Old South Shoal ....
Davis' New South Shoal
Fishing Rip, 5^ fath
Barnstable Light
Point Gammon Light
Edgartown Light
43 33.8 43 33.9 43 27.4 43 i3.4
42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42
48.4 48.4 43.0 4i.i 4i.i 39.7 39.7 38.2 38.3 36.1 34.8
32.2 3l .2
3o.4
25. I
21 .5
22.9
22 .6 12.3
19.6
19.8
00.2 o3.7 02.4 02 .0 55.8 5i.6 5i.6 5i.i 4o.2 33.5 35.5
25.2
23.4
17.4
17.0
16.4
o5.5
o4.2
58. o
o3
07.5
43.3
36.5
23.4
Longitude,
D. M.
70 1 1 . 8 70 II .7 70 19.4 70 41.2
70 48.7 / 70 48.8 ] 70 52.4 70 45.6 70 45.8 70 40.6 70 35.0 70 34.2 ) 70 34.2 J 70 39.6 70 39.5 70 46.8 70 53.6 70 5o.5
70 54 -O
71 o3.5 71 07-4 71 o3.3 70 43.6 70 53. I 70 57.1. 70 35.7 70 i4.3 70 o3.3 70 09.8 70 01 .7 70 03.9 69 56.7 69 56.6 69 56.6
69 59.3
70 53.7 70 26.7 70 02.4
70 o5.2 i,
69 57.6
70 o4.4 69 5o.o 69 5i .4 69 5 1 . 5 69 26
69 29
70 16.5 70 1 5. 6 70 29.8
REMARKS.
Trig. Point of C. S.
Newbury port Lights. Spire with Tm-rets.
Cape Ann,
Boston Bay. Gurnet South Light.
Highland Light.
Clark's Point Light. Nantucket.
Eastern Spot. Western Spot. Nantucket.
Q95^RQi
Pa«e 2.]
TABLE LIY. Corrections and Additions.
^r^ME OF PLACES.
West Chop Light
Nobska Light
Bird Island Light
Tarpauhn Cove Light
Ned's Point Light
Pahner's Ishmd Light
New Bedford, Baptist Spire
Round Hill Light
Cuttyhunk Light
Gay Head Light
No Man's Land
Newport Spire
Goat Island Light
Nayat Light
Warwick Light
Wickford Light
Providence, Baptist Church
Dutch Island Light
Beavertail Light
Point Judith Light
Watchill Light
Block Island Lie;ht
Stonington Light
Mystic Light
Say brook Light
Little Gull Island Light.
New London Light
Falkner's Island Liglit . .
New Haven Light
Stratford Point Light....
Black Rock Light ,
Sheffield Island Light .., Captain's Island Light..
Latitude.
D.
4i 4i 4i 4i 4i 4i 4i 4i 4i 4i 4i
M. 28.9 30.9
4o.i 28.1 39.0 37.6 38.2 32.3 24.8 20.9
l5.2
Plum Island Light
Montauk Light
Cedar Island Light ,
Oldfield Point Light
Eaton's Point Light
Sands Point Light
NEW YORK, City Hall..
Robin's Reef Light
Navy Yard, Flagstaff
Castle Garden, Flagstaff
Fire Island Light
Prince's Bay Light
4i 4i 4i 4o 4o 4o 4o 4o 40 40 4o 40
19.6 19.0 16.2 12.3 19.0 12.7 14.9 09.1 08.5 02.9 58.9
10.4 04.2 02.4 58.6 57.2 5i .9 42.7 39.4 42.0 42.0 37.9 3o.4
Longitude.
M.
35.8 39.0 42.7 45.1 47-4 54.2 55.3 55.0 56.7 49-8 48.5
|
4i |
29.2 |
71 |
18.5 |
|
4i |
29.6 |
71 |
19.3 |
|
4i |
43.5 |
71 |
20.0 |
|
4i |
4o.o |
71 |
22.4 |
|
4i |
34.2 |
71 |
26.0 |
|
4i |
49.6 |
71 |
24.2 |
|
4i |
29.8 |
71 |
23.9 |
|
4i |
26.9 |
71 |
23.6 |
|
4i |
21.6 |
71 |
28.6 |
|
4i |
18.2 |
71 |
5i .2 |
|
4i |
i3.4 |
71 |
34.2 |
71 54.0
71 59.0
72 20.3 72 06.1 72 o5.i 72 38.9
72 53.9
73 05.9 73 12.7 73 24.8 73 37.1
72 12.4
71 5i.i
72 i5.3
73 06.8 73 23.4
73 43.5
74 00. 1 74 o3.6
73 58.5
74 00.5
73 12.8
74 12.5
REMARKS.
Trig. Point of C. S.
Rhode Island Light
Brooklyn. New York.
TABLE LIV. Corrections and Additions.
[Page 3.
J^^ME OF PLACES.
Longitude,
REMARKS.
Sandy Hook Light
Navesink Light
Ocean House Flagstaff
Barnegat Light
Tucker's Island Light..
Cohansey Light
Egg Island Light
CajDe May Light
PHILADELPHIA, State-House
"Wilmington Light
Bombay Hook Light .
Mispilion Light
Breakwater Light
Cape Henlopen Light
Susquehanna Light
Turkey Point Light
Baltimore, Washington Monument
Poole's Island Light
North Point Lower Light
North Point Upper Light
Bodkin Light
Annapolis, State-House
Sharp's Island Light
Clay Island Light
Point Lookout Light
National Observatory
WASHINGTON City, Dome of Cap.
Fog Point Light
Assateague Light
Smith's Point Light
I Watts' Island Light
! New Point Comfort Light,
Old Point Comfort Light . .
Smith's Island Light ,.
Cape Charles
1 Cape Henry Light
D. M.
4o 27.7 4o 23.7 4o 22.8 39 46.0 39 3o.3 39 20.3 39 10.5 38 55.8
39 56.9
38 53.6 38 53.3
D. M.
73 59.8 73 58.8
73 58.2
74 06.0
74 16.8
75 21 .3 75 08.0 74 57.3
75 08.7
|
39 43.3 |
75 30.9 |
|
39 21.8 |
75 3o.3 |
|
38 56.6 |
75 18.5 |
|
38 47-9 |
75 06.1 |
|
38 46.6 |
75 04.7 |
|
39 32.4 |
76 04.8 |
|
39 26,9 |
76 00.2 |
|
39 17.8 |
76 36.6 |
|
39 17.4 |
76 i5.7 |
|
39 II .6 |
76 26.2 |
|
39 1 1. 8 |
76 27.3 |
|
39 08.0 |
76 25.1 |
|
38 58.7 |
76 29.1 |
|
38 37.7 |
76 22.6 |
|
38 i3.9 |
75 58.1 |
|
38 02.3 |
76 19.0 |
77 02.8 77 00.2
|
38 02.1 |
76 02.2 |
|
37 54.6 |
75 21 . I |
|
37 53.2 |
76 i4.o |
|
37 46.9 |
75 53.3 |
|
37 18.0 |
76 16.4 |
|
37 00.0 |
76 18. I |
|
37 07.8 |
75 52.2 |
|
37 07.3 |
75 57.9 |
|
36 55.5 |
76 00.2 |
Southern Light.
Little Egg Harbor Light.
Washingtoa.
Mouth of Potomaa
Trig. Point of C. S.
*■)*.
Page 4.]
TABLE LIV. Corrections and Additions,
J^AME OF PLACES.
KOI Devil Hill
Bodies' Island Light
Ne-R' Inlet, South Point...
Cape Hatteras Light
Ocracoke Light
Fort Pinkney
Charleston Light
SAVAKNAH, Exchange.
Cape Florida Light
Key West Light
Sand Key Light ,
MobUe, Barton's Academy
Choctaw Point Light
Grant's Light ,
Mobile Point Light ,
Sand Island Light
Biloxi Light
Pass Christian Light ,
Round Island Light ,
Cat Island Light
Ship Island West ,
Chandeleur Light
Galveston, Entrance
Galveston, Cathedral
Point Lobos
South Farallon
Point Pinos
Point Conception
Point Loma
Latitude.
D. M.
36 01 . 1 35 47-3 35 4i.i 35 i5.2 35 o6.5
32 46.4 32 4i -9
32 04.9
3o 23.8 3o 18.9 3o 17.5 3o 13.9 3o 12.9
3o o3.4
29 20.5 29 18.3
3? 47.0 37 4i.6 36 38. o 34 26.9 32 4o.2
Longitude.
|
25 39.9 |
80 o5.o |
|
24 33.0 |
81 47.3 |
|
24 27.2 |
81 51.9 |
D. M.
75 39.7 75 3i.6 75 28.5 75 30.9 75 58.9
79 ^^-^ 79 52.5
81 o5.2
|
3o |
4i |
4 |
88 |
01 |
9 |
|
do |
4o |
2 |
88 |
01 |
I |
|
3o |
17 |
6 |
88 |
07 |
5 |
|
3o |
i3 |
8 |
88 |
00 |
5 |
|
3o |
II |
3 |
88 |
02 |
0 |
88 53.1
89 14.0
88 34.1
89 08.7 88 57.0
5i.8
94 45.0 94 47.0
122 32.0
122 59.2
*
120 25.7
REMARKS.
Trig. Point of C. S. Trig. Point of C. S.
Charleston.
Trig. Point of C. S.
San Francisco Bay.
Monterey.
San Diego Bay.
[Page 5.
Stations on tJie Pacific Coast ; determined astronomically hy the U. S. Coast Survey.
STATIONS.
Latitude.
Longitude.
San Diego
San Nicolas
San Catalina
San Pedro
Prisoner's Harbor
Santa Barbara
Point Conception
San Luis Obispo
San Simeon
Point Pinos
Santa Crnz
Presidio Hill
Piinta de los Reyes
Bodega Bay
Havens' Anchorage
Mendocino City
Shelter Cove
Bucksport
Trinidad Bay
Crescent City
Telegraph Hill
Cuyler's Harbor
San Clemcnte
Ewing Harbor
Uraquah River
Cape Hancock
Point Hudson
False Dungeness
Scarborough Harbor
Lunimie Island
Astor Point
Heard's Islands, a new discovery, . -j
32
33 33 32 2i 34 M 35 35 36 36 37 3? 38 38
39 4o 4o 4i 4i 3?
4i Sy.
l4 12-
26 34- 43 19.
01 lO^ 24 24'
26 56. 10 37. 38 24' 37 59. 57 26. 47 36. 59 34. 18 20.
47 57. 18 06. 01 i3. 46 37. o3 20. AA 44'
48 06.
96 N.
71
84
59
20
71 3o 48 43 86 93 i5 20
37 87 16 67 09 o4 10 43
44 21-73 4i 45-3i 16 34-85
07 03-02
07 52 -03 21 48-78 44 01-74 II 27-61
17 i3 19 25
18 28
18 16
19 40
19 4o
20 25
20 43
21 10
21 54
22 00 22 26
22 57
23 02
23 34
23 47
24 o3
24 10
24 08
24 II
22 23
20 20
18 34
24 28
24 09
24 02
22 44
23 27
24 37
22 4o
23 49
25-00 TV
00-00
45-00
o3-oo
00-00
18-00
39-00
3i -00
22-00
25-00
10-00 i5-oo 4o-io 28-80 00-70 25-65 02-85 43 -80 07.95 13-95 19.42 27-00
00 -DO
47 -40 57-00 00-81 33-00 21.00
12-00
37.35 31.65
53 o3 53 00
73 3o E. 72 3o
Positions 0/ points in the North Pacific Ocean., prepared ly Lieut. Bent., dy direction of Commodore Perry., commander of the late expedition to Japan.
NAMES OF PLACES.
Latitude.
Longitude.
Formosa. — S. E. point
Islands, <tc. — Vele Rete Rocks
Agenhue
Lew Chew, Napha
" N. Pt. Cape Hope...
Borodino, Northern Island
" Southern Island
Disappoinlment or Rosario Island
Bonin Islands, Port Lloyd
Ponafidin or St. Peters
Lot's Wife (high rock)
Eedfield Rocks, Northern
" " Southern
Broughton Rocks
Rock Island
Japan Islands. — NirnoN, Cape Idzou
Simoda (Centre Island)
Cape Sagami
Webster Island, Yedo Bay
Treaty Building, Yoku-haina. . . .
Cape Susaki
Siriji Saki, Northern point
Teso Cape Blunt, Sangar Straits
Hakodadi, Kamida Creek
|
21 56 00 N. |
120 56 00 E |
|
21 42 00 |
120 49 00 |
|
26 32 00 |
127 12 00 |
|
26 12 00 |
127 43 00 |
|
26 48 00 |
128 16 00 |
|
25 52 00 |
i3i I 3 00 |
|
25 48 00 |
i3i 12 00 |
|
27 I 4 00 |
i4o 57 00 |
|
27 o5 00 |
142 1 5 00 |
|
3o 35 00 |
i4o 20 00 |
|
29 47 00 |
i4o 22 3o |
|
33 57 3i |
i38 49 i3 |
|
33 56 i3 |
i38 48 3i |
|
33 43 00 |
139 17 00 |
|
34 34 20 |
i38 57 10 |
|
3/i 36 o3 |
i38 5o 35 |
|
34 39 49 |
i38 57 3o |
|
35 06 3o |
139 42 45 |
|
35 18 3o |
139 4o 34 |
|
35 27 i5 |
139 4o 23 |
|
34 55 00 |
139 47 00 |
|
4r 23 00 |
i4i 3o 00 |
|
4 t 44 00 |
i4i o3 00 |
|
4i 49 00 |
i4o 47 45 |
GULF STREAM.
Under the direction of Dr. Bache, the Superintendent of the Coast Survey, the exploration of the Gulf Stream, extending from about 42° N. latitude to about 2SJ°, and from about C5j° to 80j° W. longitude, has been made— and from his notes on the same, we have extracted the following: —
The ocean within the region of the Gulf Stream is divided into several bands of higher and lower temperature, of which the axis of the Gulf Stream is the hottest, the temperature falling rapidly inshore and more slowly outside.
Thus, on a line perpendicular to the axis of the stream, drawn from Sandy Hook, the temperature at the depth of 15 fathoms and 100 miles, was 63° ; at 150 miles, 67°; at 240 miles, 63i°; 280 miles, 80 J°.
The late Lieut. G. M. Bache discovered a band of water so much colder than the rest that he called it the " Cold Wall'' S^^ cold water appearing to confine the hot water as by a wall on the inshore side. Its distance from San- dy Hook is from 230 to 280 miles; its distance from Cape May is between 132 and 178 miles: the thermometer at 15 fathoms on the Sandy Hook section rising from 62^° to 80-J°, or 18° in 50 miles; on the Cape May section rising from 62° to 83j°, or 21^° in 46 miles : at Charleston, at the depth of 20 fath- oms, rising from 67 J° to 79° in 15 miles, and at St. Simons from 70° to 76° in 12 miles, being at the rate of 4^ tenths to 9 tenths of a degree to a mile.' Be- sides this remarkable cold band there are two outside ones, suflBciently well defined, though the differences of temperature are less marked, the existence of which should be known to the navigator, that he be not perplexed in cross- ing the stream and finding warm water, to meet with cold, then warm and then cold again. The positions of these bands may be somewhat changed, when more thoroughly considered. Inside of the "Cold Wall" there is a warm laoid and then the cold water of the shore. The axis of the stream takes, in gen- eral, the curve of the coast, below rather than above the water, being turned to the eastward by the shoals off the southern coast of New England. The
GULF STREAM. 7
axis of the cold hand, the minimum of temperature which forms the "Cold Wall," follows the shore and shoals in its bendings more closely than the axis of the Gulf Stream; and is traced with considei*able probability to longitude 66°. The warm water of the Gulf Stream rests on a cold current, flowing to- wards Cape Florida, the coldest water keeping near the Atlantic coast, below the surface if not at it. By observations at several points along the coast in 400 fathoms, between Sandy Hook and Cape Florida, the surface temperature exceeding 80°, the thermometer indicated 46^° to ^b°', off Ilatteras, in 1000 fathoms, 40°.
The warm water of the Gulf Stream is of very diflfcrent depths at different points of its course, and in different parts of any one of the sections across it. From the deepest portion in the cross sections the warmer water flows off to- wards the shore, and outwards, overlying the cold. This thins out as it ap- proaches the shore, the cold water which lies at the bottom coming up in the northern sections, but the warm water prevailing to the very shore and at con- siderable depths in the southern. When the cold water is forced up by a bank or shoal, or when it comes to the surface from the thinning out of the warm, there is of course a considerable change of temperature. This cold water from the north prevails on the inside of the cold axis, at moderate depths, as far south as Hatteras, and probably to the south of it. Acting Master Jones found It, 50 miles S. E. of Charleston light, running to the S. W., the surface water being 75°, and at 20 fathoms 68°, the axis of the Gulf Stream being 82°, mo- derately warm water extending to the bottom.
The direction of the axis of the stream indicates the set of the current in that band. To the right and left of it, the current is outward and onward, and to the left as far as the Cold Wall is inward and onward. Inside of the Cold Wall, north of Cape Hatteras, and probably south of it, the current is south- erly, along the coast.
The velocity of the current in the axis of the stream, on the Cape Canaveral section, is about 3 miles per hour; on the Cape Fear section, about 2 miles per hour, and on the Sandy Hook section, about 1 mile per hour.
In the Charleston section, and to the south, the bands of cold and warm water, with scarcely an exception, are inodxiced by the sliaj^e of the hottom. The elevated portions of the bottom, forcing up the cold water into the warm, cause cold streaks, and the division into cold and warm bands.
The variations in temperature in different years and at different seasons is considerable, the more southerly sections in the same season giving usually
8 GULP STREAM.
the highest temperature. But in July, 1846, on the axis of the Gulf Stream, the temperature was higher at Sandy Hook than in June, 1853, at Canaveral, by 1 J°, and higher than at Charleston by 5j°.
The low temperatures observed, show that the Gulf Stream is comparatively a superficial current on the surface of an ocean of cold water. The tempera- tures have been observed from the surface to the depth of 500 fathoms — in a few instances as low as 13 to 1500 fathoms.
Navigators are advised to make their observations at the depth of 20 fath- oms. Saxton's metallic thermometer is highly recommended. A common Six's self-registering thermometer, or a common thermometer enveloped in cotton or other bad conducting material, allowed to remain below the surface long enough to take the temperature, will answer.
Mr. George W. Blunt in his "Atlantic Memoir" remarks —
That in summer the temperature of the Gulf water, south of Hatteras, is about the same as the water on soundings. In the months of July and August, 1845, the temperature of the water, from the Mississippi to Cape Hatteras, both in and out of the stream, even to the very mouth of the Atlantic rivers, was 84° to 82°.
The current on the western edge of the Gulf Stream, from Sandy Hook to Cape Hatteras, sets south, a little westerly, about 20 miles in 24 hours.
The current on the eastern edge of the Gulf Stream, nearly down to Mata- nilla Reef, sets to the south and west, almost opposite to the flow of the Gulf, .it an average of 20 miles in 24 hours.
For further information respecting the Gulf Stream, the navigator is referred to Dr. Bache's "Notes" on the same, in Blunt's Coast Pilot, and the "Memoir on the dangers and ice in the North Atlantic Ocean," by G. W. Blurt.
PREFACE.
In the Preface to the first edition of this work, it was observed, that the object of the publication was to collect into one volume all the rules, ex- amples, and tables, necessary for forming a complete system of practical navigation. To do this, those authors were consulted whose writings afforded the best materials for the purpose ; and such additions and improvements were introduced as were suggested \y a close attention to the subject ; and the accuracy of the tables accompanying the work was ensured by actually going through all the calculations necessary to a complete examination of them, making the last figure exact to the nearest unit. In performing this, above eight thousand errors were discovered and corrected in Moore's Practi- cal Navigator, and above two thousand in the second edition of Maskelyne's Requisite Tables. Almost all the errors in Maskelyne's collection were in the last decimal place, and in most cases would but little affect the result of any nautical calculation ; but when it is considered that most of those tables are useful in other calculations, where great accuracy is required, it v/ill not be deemed an unnecessary improvement to have corrected so great a number of small errors.
Several articles were added in the second edition, particularly the description and use of the circular instrument of reflection, methods of surveying harbors, new tables, &lc. In the third, and subsequent editions, several improvements were made, and an Appendix was given, containing methods of projecting and calculating eclipses of the moon and sun, and occultations of the fixed stars or alanets by the moon ; rules for deducing the longitude of a place from obser- vations of eclipses of the sun or occultations; a new and short method of calculating the altitude and longitude of the nonagesimal degree of the ecliptic ; solutions of several useful problems of nautical astronomy, and an improvement of Napier's rules for the solution of spheric triangles. Several new tables were added. The table of latitudes and longitudes was much increased and corrected,
A new article was given in the sixth and seventh editions, on the method of finding the latitudes by two altitudes of the same or of different objects, being
iv PREFACE.
an improvement of Mr. Ivory's solution. The method we have given is direct and simple, embracing all the cases of the problem ; a point which is not sufficiently attended to in some works of celebrity. This article is an impor tant addition to the work, and it is recommended to the consideration of navigators.
The tables, published separately in the Appendix of the first edition, are introduced into the body of this work, and are extended so as to render the use of them more simple. The first method of working a lunar observation, published in that Appendix, which has one great advantage over all other approximate methods, in the manner of applying the corrections, (all of them being additive,) is here explained and illustrated by several examples. The second is an improvement of Lyons's method, which had been known for many years, but had not been generally used, because the tables were not sufficient- ly extended. This difficulty is now obviated, by means of Tables XLVII. XLVIIL, which have been compared with Thompson's tables, and many of them recomputed by the aid of Shephard's tables. The third method was given by the author of this work, in 1795. The fourth method is an improve- ment of Witchell's process, in which, without altering materially the calcula- tion, the number of cases is considerably reduced.
Any person who wishes to examine the tables, may do it by the methods used for that purpose, which will here be explained, with some additional remarks :
Tables I. and II. were calculated by the natural sines taken from the fourth edition of Sherwin's logarithms, which were previously examined, by differ- ences ; when the proof-sheets of the first edition were examined, the numbers were again calculated by the natural sines in the second edition of Button's logarithms ; and if any difference was found, the numbers were calculated a third time by Taylor's logarithms.
Table III. contains the meridional parts for every degree and minute of the quadrant, calculated by the following rule, viz.
M =:r T X 0.000791 57044G8, in which T is the log. tangent less radius of half the latitude, increased by 45°, taken to seven places of figures, reckoned as integers; and M is the meridional parts of that latitude in miles.
Table IV. contains the declination of the sun, which was compared with the Nautical Almanacs for the years *1 833, 1834, 1835, and 1836, and marked to the nearest minute.
Table IV. A. The equation of time, for the years *1833, 1834, 1835, and 1836.
Table V. contains the correction of the sun's declination, as published by Dr. Maskelyne. The correction taken from this table will rarely differ more
than sixteen or seventeen seconds from the truth.
* Altered to correspond to the yeiirs 1848, 1840, 1850, and 1351.
PREFACE. \
Table VI. contains the mean of the sun's right ascension, taken from the Nautical Almanacs for the years 1833, 1S34, 1835, and 1830.
Table VI. A. contains the correction for the daily variation of the equation of time
Table VII. contains the amplitudes of the sun for various latitudes and declinations, calculated by Taylor's logarithms, by this rule :
Log. scc.lat.-|-log. sine declination — lO.OOOOOOOrrlog. sine amplitude.
Table VI II. contains the right ascensions and declinations of one hundred and eighty stars of the first, second, and third magnitudes, with their annual variations, adapted to the beginning of the year 1830. This table was abridged from that published by the astronomer royal at Greenwich, (Mr. Pond,) in the year 1833.
Table IX. contains the time of the sun's rising and setting, calculated by Taylor's logarithms, by this rule :
Log. COS. hour = log. tang, declin.-j- log. tang. latitude — 10.0000000.
Table X. contains the distances at which any object is visible at sea. calcu- lated by the rule given in § 195 of Vince's Astronomy, in which the terrestrial refraction is noticed. This circumstance was neglected by Robertson. Moore, and others, and of course their tables are erroneous. The rule given by Mr. Vince, expressed. in logarithms, is this:
0.12155 -f- half log. of height in feet = log. of dist. in statute miles. In reducing the rule to logarithms, the radius of the earth was called 20911790 feet, which agrees nearly with the mean value given in De La Lande's Astronomy.
Table XI. is a common table of proportional parts, the construction of which does not need any explanation.
Table XII. contains the refraction of the heavenly bodies, calculated by Dr. Bradley's rule, supposing the refraction to be as the tangent of the apparent zenith distance of the object, decreased by three times the refraction, the horizontal refraction being supposed equal to 33'. The rule, expressed in logarithms, is this :
Log. tang. (app. zen. dist. — 3. refraction) — 8. 2438534= log. of ref in sec. The numbers calculated by this rule agree nearly with those published in Table 1 of Maskelyne's Requisite Tables.
Table XIII. contains the dip of the horizon for various heights, calculated by the rule in ^ 197 of Vince's Astronomy, in which the terrestrial refraction is allowed for. All the numbers of this table differ a little from those published by Dr. Maskelyne, who had made a different allowance for that refraction. The rule given by Mr. Vince, expressed in logarithms, is,
1.7712711 -f- half the log. of the height in feet = log. dip in seconds.
Table XIV. contains the sun's parallax in altitude, calculated by multiplying
vi PREFACE.
the natural sine of the apparent zenith distance by the sun's horizontal parallax 8f '. The numbers in this table agree with those published by Dr. Maskelyne.
Table XV. contains the
Augmentation of the moon's semi-diameter = 15".626 X sine J)' s altitude. This table agrees nearly with that published by Maskelyne.
Table XVI. contains the dip for various distances and heights, calculated by this rule,
D = -d4- 0.56514 X -'
in which D represents the dip in miles or minutes, d the distance of the land in sea miles, and h the height of the eye of the observer in feet.
Tables XVII., XVIII., and XIX. , were first calculated by the author of this work, and published in the Appendix to the first edition. The correction in the first of these tables is equal to the difference between the star's refraction and CO'. The correction of Table XVIII. is equal to the diiference between 60' and the correction of the sun's altitude for parallax and refraction. The correction of Table XIX. is equal to the difference between 59' 42" and the correction of the moon's altitude for parallax and refraction. The logarithms in each of these tables may be found by adding together the constant log. 9.6990, the log. cosine of the apparent altitude of the object, the proportional logarithm of the correction of the altitude of the object for parallax and refraction, and rejecting 20 from the index. The methods of performing these calculations are so obvious, that it is unnecessary to enter into any further explanation. Most of the numbers in these tables were calculated three different times.
Table XX. Corrections in seconds,