HISTORY OF GEOLOGICAL SURVEY. 47 



was performed under the direction of Prof. Quimby. The map shows 

 the courses of all the valuable mineral veins existing upon the tract, as 

 well as the remarkable windings and dislocations of the formations which 

 are there exhibited. Not less than five hundred specimens were collected 

 to illustrate this map. 



A Trigonometrical Survey. 



By an act passed in 1871, congress authorized the coast survey to 

 expend a considerable sum of money in extending their triangulations 

 into the interior, but only for those states where a geological survey is in 

 progress. New Hampshire is the only one of the New England states 

 which has so far received any benefit from this act, and the annual appro- 

 priation for this purpose has not been less than $2,000. The work has 

 been placed in the hands of Professor E. T. Quimby, of Dartmouth 

 college. He first occupied the stations established in 1869 for the benefit 

 of the geological survey, so as to verify their accuracy. The work has 

 been successfully carried on now for three seasons, and the latitudes and 

 longitudes thus obtained are given in the chapter on topography. 



Levelling along Connecticut River. 



For the sake of a proper understanding of the surface geology of 

 Connecticut river, it has been thought best to level from the Massachu- 

 setts line to Connecticut lake. The work was commenced in 1870 by 

 Gyles Merrill, Jr., and S. Q. Robinson, of the class of 1872, C. S. D., 

 Dartmouth college. They have levelled between the line and Walpole. 

 Mr. Merrill was assisted also by his brother. The line from Bellows 

 Falls to Windsor was levelled by Warren Upham in 1874. The work 

 above Hanover was performed in 1871, under the direction of A. F. Reed, 

 of Groton, Mass., assisted between Hanover and Lancaster by Dr. Nathan 

 Barrows, of Meriden, and between Lancaster and Connecticut lake by 

 Messrs. C: F. and F. A. Bradley, of the class of 1873, Dartmouth college. 

 The connection between this survey and that of the P. & O. Railroad, at 

 Dalton, was made by J. T. Woodbury in 1874. 



In the report for 1871 there appears a long list of altitudes, including 

 all that had been obtained by special surveys at that time. These are 

 to be given more fully in a following chapter, with many additions and 

 improvements. 



