HISTORY OF GEOLOGICAL SURVEY. 23 



Woolson of Lisbon, two square miles of the territory were surveyed. 

 The intention was to set stakes at the corners of every block of five 

 hundred feet square, and thus to locate the formations with great 

 definiteness. 



At the request of the commissioners appointed to consider the propri- 

 ety of establishing a survey of the water-power of New Hampshire, we 

 prepared a map of the state, upon the scale of ten miles to the inch, 

 showing by colors the areas drained respectively by the Connecticut, 

 Androscoggin, Saco, Piscataqua, and Merrimack rivers. It was compiled 

 from our data by Mr. Huntington. The map accompanied the report of 

 the hydrographic commissioners. A copy from the same plate, with 

 changes and additions, was presented with our second report, designed 

 to illustrate the distribution of the granite and the progress of our trian- 

 gulation, as well as some of the geological formations. 



Measuring Heights. 



In May, 1870, a trip was taken by Mr. Huntington to determine the 

 relative altitudes of the passes along the principal White Mountain range 

 between the Crawford house and Waterville. The snow had not entirely 

 disappeared, so that the expedition was of a very laborious character. 

 The results are given elsewhere. 



A thorough knowledge of the general elevation of the land of the state 

 being very important, measures were taken early towards the obtaining 

 of exact altitudes in the interior. Upon examining various railroad 

 surveys, discrepancies appeared, so that they could not be relied upon. 

 Two lines of survey running lengthwise of the state were therefore 

 devised, one from Portsmouth (or Great bay) through Manchester, Con- 

 cord, and the Connecticut valley to Connecticut lake ; the other from 

 Lowell, Mass., to connect with the other survey at Lancaster. The 

 final conclusions appear in another chapter; but the work was com- 

 menced early in the second season. Messrs. Frank and H. D. Wood- 

 bridge, of Dartmouth college, obtained, by actual levelling much of the 

 way, facts which fixed the height of the barometer at the Shattuck obser- 

 vatory, in Hanover, at 60371 feet above mean tide-water. A few com- 

 putations were made, also, by a comparison of barometical observations 

 at the Shattuck observatory, and the top of Mt. Moosilauke. 



