GEOGEAPHICAL POSITIONS 



67 



THE UNITED STATES. 



LAT. N. 



LONG. W. 



Cape Small 



Portland Head, Lighthouse 

 Cape Elizabeth, East Light 

 Fletcher's Neck, Light on 



Wood Island 



Cape Porpoise Harbour, 



Light on Goat Island . 

 Cape Neddick, Lighthouse 

 York Harbour, Light on 



Boon Island 



New Hampshire. 



Agamenticus Hill, summit 

 Portsmouth Harb., Whales 



Back Light 



Isles of Shoals, White Id., 

 Lighthouse 



AUTHOBITIES. 



Massachusetts. 



Newbury Port, East Light 

 on Plum Island 



Cape Ann, North Light on 

 Thatcher Island 

 Light on East point 



Baker's Island, Lighthouse 



Marblehead, Light at the 

 entrance 



Nahant Head 



Boston, State House... [1] 

 Cimard Wharf, Flagstaff 

 Cambridge Observatory, 

 Dome [2] 



Boston Bay, Lighthouse 



on Little Brewster Id. 



Minot's Ledge, Light ... 



Scituate Harbour, Light on 

 North Point , 



Pljmouth Harbour, Light 

 on North side of entrance 



Sandwich, Church Spire... 



Barnstaple, Sandy Neck, 

 Lighthouse 



Billingsgate Point, Lt.-ho. 



Cape Cod, Provincetown, 



Orthodox Church Spire 



Race Point, Lighthouse 



Highlands Lighthouse 



Nausett, Centre Light 



Monomoy Island, 

 house at South end 



42 58 



42 48 25 



42 38 19 

 42 34 47 

 42 32 10 



42 30 18 

 42 25 

 42 21 28 

 42 21 48 



42 22 48 



42 19 89 

 42 16 9 



42 12 15 



42 12 

 41 45 26 



41 43 20 



Light- 



70 19 45 



70 25 31 

 70 35 30 



70 28 36 



70 41 41 

 70 41 48 

 70 37 25 



70 49 6 



70 34 30 

 70 39 53 

 70 47 10 



70 50 2 



70 54 30 



71 3 

 71 2 



50 

 30 



71 7 39 



70 53 25 

 70 45 34 



70 42 55 



70 36 4 

 70 29 10 



70 16 52 

 70 4 9 



70 11 

 70 14 

 70 3 

 69 57 



31 



36 



39 



4 



The Triangttlation made 

 for the United States Coast 

 Survey, under the superin- 

 tendence of Professor A. D. 

 14 30 Bache, &c. 



Fear. Section V., from Cape 

 Fear to St. Mary's River. 

 Section VI., from St. Mary 'a 

 River to St. Joseph's Bay. 

 Section VII., from St. Joseph's 

 Bay to Mobile Bay. Section 

 VIII., from Mobile Bay to Ver- 

 milion Bay. Section IX., from 

 Vermilion Bay to the Rio 

 Grande. Section X., Coast of 

 California, San Diego Bay to 

 42nd parallel. Section XI., Coast 

 of Oregon, &o., 42ud to 49th 

 parallel. The Tables give the 

 latitudes and longitudes of some 

 of the trigonometrical points in 

 each section. The manner in 

 which these data have beau ob- 

 tained may be briefly explained 

 here. 



14 5 



13 45 



13 30 



12 35 



13 15 



69 59 38 



In each section a base line of 

 from 5 to 10 miles in length 

 was measured with all posoible 

 accuracy. A series of triangles, 

 deriving the length of their sides 

 from this base, was then esta- 

 blished along the coast, by the 

 measurement of the angles be- 

 tween the intervisible stations. 

 In this primary series the tri- 

 angles were made as large as 

 the nature of the country would 

 permit, because the liability to 

 error increases with the number 

 of triangles. 



On the bases furnished by the 

 sides of the primary triangles, a 

 secondary triangulation was 

 next established, extending 

 along the coast, and over the 

 smaller bays and sounds, and 

 determining a large niunber 

 of points at distances of a few 

 miles apart. 



The distances between the 

 points thus determined, were 

 liable to an average error of 

 about one foot in six miles. 



As, on the completion of the 

 primary triangulation in each 

 section, the several series form 



