108 GREEN MOUNTAINS IN MASSACHUSETTS. 



No detailed geological study of the Hoosac tunnel seems to have been 

 published, which is remarkable considering the importance of this engineer- 

 ing work and the number of experts who examined it when in construction. 



In the reports of Profs. James Hall and T. Sterry Hunt as -experts 1 the 

 general distribution of the rocks in the tunnel is correctly given. Prof. 

 Hall noticed the transition from white gneiss to granitoid gneiss at the west 

 edge of the latter rock, and also speaks of the micaceous gneiss at the west 

 portal "resting against or upon the limestone," an exposure no longer visible. 



Massachusetts House Document No. it, January, 1875, Appendix. 



