 being located on top of a natural hill site whose slope directs the flow in an upward direction, so that the said angular relationship between the helicoid axes and the flow vector is secured on {HEAD ~ account} of {TAIL ~ the chosen location} 
of
being located on top of a natural hill site whose slope directs the flow in an upward direction , so that the said angular relationship between the helicoid axes and the flow vector is secured on { HEAD ~ account } of { TAIL ~ the chosen location }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL