Line as pictorial element: rhythm,pattern &structure

I missed the first drawing evening class of the year with a chest infection ( and the last 2 of last term for other reasons) so I arrived really early this evening in anticipation. Some familiar faces, some new , it was great to get stuck in to some line drawing with pen. In the first exercise ( above) we were drawing a curvy line then drawing lines very close together following it, even closer in the inner curves ( a good tip was to make small guide marks in the curves -it was so easy to lose the plot!) Interesting patterns soon began to emerge - very sixties!
The second exercise was to draw around obstructions. As I was using the thicker end of a double-ended permanent marker, the back looked even more interesting because of the variation in pressure.

For the final hour we were doing observational drawings of shells or bark using the techniques we'd practiced. Yes it's that shell again - I could have chosen a different one but there's something about the familiarity of drawing the same subject repeatedly but using varied materials and methods. Or am I just getting set in my ways....