80 THE MAKQrETTE IKON BEAllING DISTRICT. 



(3) The baiiuings sbow foldings and contortions. 



(4) Tliejaspilite and ore are jointed and sliow cleavage. 



(.")) The associated rocks are seilinientary, and on account of the alternation 

 with schists, the ore and jasi)ilitc, as well as the schists, must be metamorpbosed 

 sedimentary rocks. 



(t>) The i)reseuce of phosphoric acid. 



Tliesc arguments are then taken tip and discussed separately. That 

 nviiuliert'd (1) is summarily dismissed as no argument. We will let the 

 author himself reply t(.) the others. 



(2) The banding and lamination of the jaspilite and ore do not appear to us to 

 be proof of sedimentary origin, since a similar banding is strongly marked in the 

 rbyolites the modern lavas approaching nearest the jaspilite, in dikes of felsite, in 

 furnace slags, etc. * * * This structure is common to botb sedimentary and 

 eruptive rocks, lience per se is of no value either way. The structure of the banding- 

 does often show the origin of the rock wben it lias been studied with care. Those 

 advocating the sedimentary origin of the above mentioned ore have rested their claim 

 on the simple fact that the rock was "striped," and not on the character of the 

 banding. We have studied the banding and can find nothing in it that proves 

 sedimentation or is inconsistent with that repeatedly seen by us in known eruptive 

 rocks. 



(3) The folding and contortion of the banding would take place in any rock 

 whatever its origin, after it was in position, if subjected to proper conditions. * * * 

 Hence folding and contortion of banding in rocks, like the banding, is common to 

 both sedimentary and erui>tive rocks, and like the latter (banding) is no proof of 

 either origin. 



(4) Joints and cleavage planes are well known to be common to both sedimen- 

 tary and ernptive rocks, hence their presence can not be taken as i)roof of either 

 origin. 



(5) Wlioever advanced the view that since the associated rocks were sedimentary, 

 therefore the jaspilite and ore must be, * * * nuist have been aware that this 

 principle would prove the great majority of dikes and veins to be sedimentary. A dike 

 jiassing through slate nuist be sedimentary because the slate is sedimentary. * * * 



(6) The presence of phosphoric acid could only have been taken as proof of 

 sedimentary origin by those who had no knowledge of eruptive rocks, since it is well 

 known to occur in many of the latter. * * * 



We have now taken up all the evidence which we are aware has been used to 

 prove the sedimentary origin of the jaspilite and ore. The characters used as proof 

 seem to be such as are conunon to both sedimentary and eruptive rocks or are of no 

 weight. (Pp. 473-475.) 



