xiv PREFACE. 



had contributed largely to the sum of the work. ITis early death in 1886 

 deprived the Survey of one of its most accurate and thoughtful geologists. 



The third part deals with the Greylock synclinorium — made up of the 

 Cambrian-Silurian quartzite, limestones, and schists, which are the offshore 

 time equivalents of the white gneisses and schists of Hoosac mountain. 

 The field work was done by Mr. T. Nelson Dale, assisted in part of the 

 area by Mr. William H. Hobbs. The analysis of the results and the pre- 

 sentation are by Mr. Dale. 



As during the first two years we had not yet the benefit of the new 

 topographic map of Massachusetts, our work was delayed by the necessity 

 of making our own maps. This was done in part by Messrs. Putnam and 

 Wolff, assisted by Mr. Yocum. Later, Mr. Josiah Pierce made a detailed 

 topographic survey of the western flank of Hoosac mountain which forms 

 the geographic basis of PI. iv. 



Mr. C. L. Whittle was also connected with the work under Dr. Wolff 

 during the season of 1887. 



Mr. William H. Hobbs acted as assistant to Mr. Dale during one season 

 and a part of another in the work on Greylock and was engaged inde- 

 pendently during the rest of the second season on the coloring of the 

 northwestern part of the Greylock sheet. 



I have mentioned in its proper place the fact that we owe to Mr. C. D. 

 Walcott the determination of the age of our basal quartzite. 



R. P. 



