258 Pirsson and Washington — Geology of Red Hill, N. H. 



also iron pyrites and tourmaline, the last mineral being mis- 

 taken for coal. The writer has not found any tourmaline and 

 its occurrence in such amount that it could be mistaken for 

 coal seems improbable. 



The next description of Eed Hill is by Prof. C. T. Hitch- 

 cock,* who calls the rock a true syenite and collates it with that 

 of the Belknap Mts. at the other end of Lake Winnepesaukee. 

 He states that its contact with the enclosing gneiss may be seen 

 at the north end in Sandwich. Hitchcock also mentions that 

 the enclosing gneiss is cut by feldspathic dikes at a distance 

 from the syenite. The latter is thought to have come up 

 through a fault along a synclinal axis. Mention of glacial 

 phenomena in relation to the mountain is also made. 



The first petrographical work on the Red Hill s} 7 enite was 

 done by Hawes,f who described the syenite as consisting of 

 orthoclase and hornblende. Details of these and of other 

 accessory minerals are given and the presence of some inter- 

 stitial quartz is mentioned. 



Later Bayley^: gave a detailed petrographic description of 

 some hand-specimens of the syenite which had been sent to 

 him, accompanied by a chemical analysis of the rock by Hille- 

 brand. He showed that the rock was not quartzose, as sup- 

 posed by Hawes, but contained nephelite and sodalite and 

 should therefore be classed with the nephelite syenites. His 

 work will be referred to in detail later. 



From what has been stated above, it will be seen that up to 

 the present the geology of Red Hill has never been studied in 

 any adequate manner, while the recognition by Bay ley of the 

 alkalic nature of the massif, combined with the mention of 

 trap dikes by those who had visited it, seemed to point to an 

 assemblage of igneous rocks which it would be of interest to 

 investigate in the field and in the laboratoiw. This has been 

 done with the results set forth in the following pages. 



The Map. — The topographic base of the accompanying 

 geologic map has been compiled by the writer from various 

 sources including his own notes. The geologic outlines laid 

 clown upon it are in some places correct, in others as nearly 

 correct as the heavy mantle of drift and of debris which 

 covers parts of the area permit. 



General Geology. 



Topography. — Red Hill is a quite regular oval mass about 

 4 miles long by 2"5 broad at its base. Its highest point is a 

 little over 2000 feet above sea-level and about 1500 above the 



* Geologv of New Hampshire 18TT, vol. ii, p. 605, vol. iii, p. 132. 

 f Ibid.. Pt. IV, 1878. Mineralogy and Lithology, p. 206. 

 JBull. Geol. Soc. Am,, vol. iii, p. 243, 1892. 



