j(y NEW YORK STATE MUSEUM 



bu.ried channels beneath the drift, {h) the character and depth of 

 the drift, (c) the kind of bed rock, (c?) the condition of bed rock 

 for construction and permanence of tunnel, (c') the underground 

 water circulation, (/) the occurrence of folds and faults, (^) the 

 position of weak zones, (/z) the depth required for substantial con- 

 ditions, and many other similar problems. 



These need not be treated in their original form. Indeed many 

 of them have now ceased to be problems in any real sense, for sub- 

 sequent provings have made them simple facts, and wholly new 

 questions came to take their places. In some of the larger prob- 

 lems, however, it is believed that a treatment which involves a dis- 

 cussion of the original problem and the method of solving it, to- 

 gether with the data thus secured and the final interpretation of 

 geologic features as now understood or established will be more 

 instructive than a mere enumeration of the collected results. 



So far as possible each problem is treated as a unit and fully 

 enough to be understood by itself. But a general knowledge of 

 local geology as outlined in part i is assumed. 



