34^ APPENDIX TO PARTS I AND II. 



APPENDIX B. 



Altitudes, Contour Lines, and Raised Maps. 



During all our explorations of the state for the study of its geology and the collection 

 of rock-specimens, frequent barometric measurements have been also obtained, and the 

 prominent topographic features of the country have been carefully noted. Only a small 

 portion of all the heights thus measured appear in Volume I (pp. 210, 211, and 242, 

 chap. X, and pp. 304-314), the altitudes there given being those of mountains, villages, 

 ponds, or other points of special interest. Since the publication of that volume, many 

 additional barometric observations have been made. 



The information thus gathered respecting the configuration of the state, although 

 incomplete because it has been impossible to make a detailed examination of our entire 

 territory, yet seemed worth preservation, and sufficient to justify an attempt to present 

 contour lines on the new map accompanying this report. Numerous series of altitudes, 

 accurately determined by surveys for railroads, or by levelling done specially for the 

 geological survey, have formed a basis to which the barometric measurements have 

 been referred. According to these observed heights, and others estimated for adjacent 

 hills and valleys, lines of contour for each one hundred feet above the sea were first 

 drawn on the county maps of large scale, which had been used in our explorations, and 

 thence were transferred to the draft of the new map. These lines have been engraved 

 separately from the rest of the map, so that they may be printed in a color different from 

 that of the streams, roads, boundary-lines, names, etc. They are thus easily distin- 

 guished from all other lines, but are required to be printed separately, so that they are 

 liable to slight misplacement, sometimes making streams and contour lines disagree in 

 their positions. These contours not only show the place, shape, and height of separate 

 mountains and hills, but permit a comparison of their heights above the sea and in rela- 

 tion to each other throughout the whole state. For convenience in such comparison, 

 the lines of 500, 1,000, 1,500 feet, etc., above the sea are dotted, and their heights fre- 

 quently marked, while the other lines are continuous and unmarked. 



The eastern part of Rockingham county, and the portion of Essex county, Mass., 

 which comes within the limit of our map, being occupied more or less fully by the re- 

 markable lenticular hills of glacial drift, have received special attention. Contour lines 

 are shown upon these areas for each 50 feet, those marking heights 100, 200, and 300 

 feet above the sea being continuous lines, while those intermediate are dotted. The 

 Ammonoosuc mining district has been surveyed by Mr. John N. McClintock, whose 

 map with contour lines for each 10 feet is presented in Part V of this report. Besides 

 these, the White Mountain district has perhaps been as well represented as any other 

 portion of the state ; but many of the smaller peaks, ridges, spurs, and ravines remain 

 to be explored and mapped in this region. It is hoped that our efforts to show the 



