GEOGRAPHY AND ANTIQUITIES. 353 



purpose of verification. We have then passed, in five years, on the 

 primary. triangulation, from Rhode Island to Maine ; and it could have 

 been done in three years, had it been desirable so to occupy the time. 



" The secondary triangulation has extended along the coast, deter- 

 mining the positions of points near the coast, around the peninsula of 

 Cape Cod to Cape Ann. There are now two parties at work upon this 

 step in the process; one passing from Cape Ann to Newburyport, and 

 the other from \e\vbury port to Portsmouth ; so that by the end of the 

 season we shall have reached nearly to Saco, in Maine, with our secon- 

 dary triangulation. 



" The topography has been carried regularly forward in the same 

 way, with but one exception, in which I have perhaps taken some re- 

 sponsibility. I certainly did have Boston Harbor surveyed two years 

 before it would have been done in the regular course. But then 1 had 

 a very violent motive for this ; namely, an appropriation made by the 

 State of Massachusetts to hasten the survey of the coast, an act of 

 liberality which has never been imitated by any other State in the 

 Union. We have two large manuscript maps of Boston Harbor, which 

 you will see in the State-House, in the month of October next, of a 

 very finished character. Thus, in six years (adding the present year), 

 at this end of the work, we have advanced from Point Judith, with the 

 primary triangulation, to Portland : with the secondary, beyond Ports- 

 mouth; and with the topography, to Gloucester. 



" The hydrographers have had a long and difficult piece of work in 

 this section. They have had those famous Nantucket Shoals to stop 

 them. But if the survey had rendered no other benefit to the coun- 

 try than making known the before unknown and hidden dangers of 

 that part of the coast, it certainly would have repaid to the country, 

 in money, the whole amount which it has cost. One vessel which 

 came very near stranding upon shoals now, through the enterprise of 

 Lieut. Davis, made known and familiar to us had a cargo which paid 

 the government a duty of $125,000: and if this sum had been de- 

 voted to the survey, the shoal would have been discovered years ago. 



-M V V * * * 



Lieut. Davis's discoveries consist of an important shoal outside of 

 the Old South Shoal of Nantucket, lying right in the track of vessels 

 from New York to Europe, and returning, and of vessels passing 

 from the New England States to the Southern States and South 

 America. The hydrography has been extended up Buzzard's Bay 

 through Nantucket Sound, through the Vineyard Sound, has em- 

 braced the Nantucket Shoals, and has included the hydrography of 

 Boston Harbor, of which an accurate chart has been made. The re- 

 sults of the survey pass through a regular process, from the time 

 the observations are made in the field to the time the map is produced 

 in the office. The assistants, who make the observations, report 

 them, and compute them. Other computers also pass over the same 

 calculations. The results are brought into juxtaposition and compared. 

 If they agree, they are considered as correct. If they disagree, the 

 cause is carefully examined, and the error corrected. The "results, 

 thus verified, are placed upon paper in the ordinary forms of projec= 

 tion of maps. They are next engraved, as fast as we can find hands 



30* 



