96 THE MAUQLTETTE IROX-BEAIIING DISTKICT. 



lig'btest ])articles were waslu'd away from the neighborhood of the couceii- 

 trates. Tlius the ores uj)sti-eaiii grade into k'ss pure ores farther down- 

 stream, and these into beds containing no ore. The section iUustrated in 

 fig. 3 was supposed to lend aid to this view. 



The four lenses shown in the section, vrith the intercalated seams of chloritic 

 schist, suggest in their arrangement the false bedding or cross bedding sometimes 

 found in sandstone strata. This false bedding is due to the actiou of ruuniug water 

 depositing sediment in successive layers on a sloping bank. * * * For example, 

 during and after a freshet any stream heavily charged with sediment will deposit 

 beds of sand having this structure in the pools and wider portions of its l)ed. 



According- to this tlieorv, maguetitic or hmouitic sand would be deposited 

 even Avhere the current Avas .swift, while tlie more common sand and clay 

 Avould be carried onward. After the freshet, when- the Aelocity of the stream 



-^zr-tr^^ErEOireofion of old Current r^ 



Fig. 'A. — Cross-section throngli ore liodies at the Edwiirds miue. 



decreased, the lighter substance svould be deposited n])on the iron sand, and 

 this, when metamorphosed, would give rise to various schists. During sub- 

 secjuent freshets most of the lighter material would be washed away, leaving 

 the ore bodies covered with a thin film of mud or sand. "The lighter 'tails' 

 of the deposit being- swejjt awav, there would be left a place for a new 

 deposit of ore beyond and ovei'lappiiig the older one." The distribution of 

 the ore bodies of the Pjdwards mine is thought to correspond in all respects 

 to the distriV)ution e.N])ected of deposits thus formed; "the pure t)re is in 

 each case at the head and the mixed ore at the tail of the natural puddle, as 

 indicated in the sketch." When the ore lenses consist partly of magnetite 

 and ])artlv of sj)ecular ore, the former is found at the head, the latter iu the 

 middle, and mixed ore at the tail of each lens. This theory is intended to 

 explain more particularly the manner of concentration of the hard ore on 



