Grindstone Island is just opposite the St. Lawrence River village of Clayton. There are no official roads. Folks get around in old jalopies or ATVs. Only 11 people winter on Grindstone, but families who’ve spent generations of summers there return, and a larger community reassembles. On Saturday nights, the place to be is the big dance at Dodge Hall. Usually it’s DJs or rock ‘n’ roll bands who supply the music. But every once in a while, some fiddlers and callers get together for an old-fashioned square dance. David Sommerstein joined in.