GENERAL GEOLOGY OF THE DISTRICT. 447 



to have been somewhat irregular (Fig. 7), and between it and the ordinary 

 slates is a layer of basal conglomerate varying from a few inches to several 

 feet in thickness. It, however, quickly grades into the ordinary slate of the 

 district, as though this place were at the bottom of a comparatively level 

 shallow sea, rather than adjacent to a shore. This cough )nierate contains a 

 few white ([uartz and jasper pebbles, the former sometimes being ten inches 

 in diameter; but the great mass of tlie fragments, and especiallv all of the 

 large bowlders (which reach occasionally live feet in greatest length), are 

 from the underlying green schist. Moreover, the conglomei'ate proves that 

 the schistose character of the underlv^ing rock had been fully attained 

 before the deposition of the slates ; for the schistose structure of the frag- 

 ments is as well developed as in the ledge below. A fragment broken 

 from such a schist is naturally longer in the direction of its tibers than 

 transverse to them. That the matei'ial does break in tliis manner was 

 proved in obtaining specimens. The green schist fragments of the con- 

 glomerate are generally longest in the direction of schistositv. Now, frag- 

 ments of this sort, when liroken from the basement i-ock and laid down as 

 a part of the conglomerate, would naturally lie with their longer direction 

 parallel to the horizon; and this has been the case, for, as shown in Fig 7, 

 nearly all of the larger fragments lie with their greatest length parallel to 

 the then sea floor, that is, the schistose structure of the fraf/inoits is at ri(/ht 

 anples to that of the leclqe from ivhich they were derived. Now, if this schistose 

 structure had been develo})ed subsequently to the formation of the conglom- 

 erate, it would have been parallel in both the fragments and basement 

 rocks. So far as a l)asal conglomerate and unconformit\' in structure at a 

 single place can indicate a time gap between two formations, this locality 

 indicates it. If the underlying rock was a sedimentarv one it must have 

 been folded and extensively eroded to change it to a crystalline schist and 

 bring its foliation in a vertical po.sition at surface. If it was an eruptive 

 rock it has been most profoundly altered, and its alteration, as just shown, 

 must have taken place before the formation of the conglomerate. Such an 

 alteration would hardlv take less tiuic than its transformaticm from a clastic. 

 So in whatever light it is regarded this l»asriiu'Ut rock is vastly older than 

 the conglomerate and slates which rest upon it. 



