74 AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



The least rise of tides is at Cape Florida, Cape Hatteras, and near the east end 

 of N'antucket, the greatest at Tybec entrance, New York entrance, Boston and the 

 Bay of Fundy stations. 



The physical features of the coast clearly marked out are the great Southern 

 Bay between Cape Florida and Cape Hatteras, the great Middle bay between Cape 

 Hatteras and Nantucket, and the Eastern bay between Nantucket and Cape Sable, 

 which itself may be part of the great Eastern bay between Nantucket and New- 

 foundland. This form of the coast, has, of course, not escaped the attention of 

 geogi-apiiers. 



The tides are lowest at the entrance of these bays and rise as they pass into and 

 up them. 



Massachusetts bay is a dependency of the eastern bay, and so is Fundy. These 

 interior bays, as also the sounds freely open to the sea along the, coast present the 

 same features in their tides. Chesapeake bay, widening and changing direction 

 from the entrance, is an exception to the rule. Nantucket and the Vinyard Sounds, 

 Buzzard's bay, Narragansett bay. Long Island Sound, New York Bay, and Delaware 

 Bay, come under the rule. 



NOTES ON THE MEASURKMEVT OF A BASE FOR THE PRIMARY TRIANGULATION OF THB 

 EASTERN SECTION OF THE COAST OF THE UNITED STATES, ON EPPING PLAINS, MAINE. 

 BY A. D. BACHE, SUPERINTENDENT OF THE U. S. COAST SURVEY. 



(^Ab^tract for the Canadian Journal, communicated hy the Author.) 



The reeonnoissance for a base of verification at the eastern extremity of the 

 primary triangulation in section I. of the coast wa,s commenced by Chas. O'Bou- 

 telle, Esq., and Major Henry Prince, TJ. S. A., Assistants in the Coast Survey in 

 1853, and continued through 1854 and 55. The absence of long and straight 

 beaches on this coast rendered it absolutely necessary to look for an interior site. 



The reeonnoissance resulted in the selection of Epping Plains, Penobscot Co., 

 Me., as the most suitable site for the purpose, considering the character of the 

 g^'ound itself, and the facility of connecting the ends of the base with the primary 

 triangulation. 



In 1856 I examined the site and took steps to obtain the necessary estimate of 

 the cost of preparing it for measurement. The profile of the road as graded gives 

 a good general idea of the ground, as it varied but little from the natural profile. 



The whole length of the line is about 8719 metres, or 5.4 miles. Its general 

 direction is E 41f N (true bearing). From the eastern end for about 4 miles the 

 plain is quite level, rising in the first mile pretty regularly about 15 feet, descend- 

 ing nearly as much in the second to rise by the same quantity in the third. It 

 then runs along an elevated level for a fourth of a mile and descends gradually to 

 the rougher part of the base which is included between the 8| miles from the east 

 end and western end of the base. 



This line was skilfully graded by Mr. Boutelle so as to follow the natural surface 

 where the grades did not run above three degrees, and to give as long slopes as 

 possible of the same grade for the convenience of measurement. 



The graders partly consisted of the farmers and lumber men of the district, who 

 served with great cheerfulness and skill in the use of the heavy implements for 

 rough 'gradmg. One of the greatest difficulties was the removal of such boulders 



