This book is exactly what I was looking for!! At another site (
http://books.google.com/books?id=Lyi...page&q&f=false) you can actually view the first 14 pages. In these pages it is shown how Rattlesnake Island was part of a ring dike (page 13) connected with the Belnap Mts...fascinating!! I previously thought that the Ossippee Mts were the only ring dike in NH. I just ordered the whole book (70 pages). Thanks so much for pointing me in the right direction.