Perpendicular

This Comet Windmill can be seen all over the Australian Outback, its founder was Sydney Williams, the manufacturing facility was established in Dulwich Hill Sydney in the 1920's.
It was the most up to date Windmill Factory in Australia at the time. They were the sole choice on all major stock routes.
Today we have the wind turbine farms, but in rural and most country areas you will see this old Comet Windmill.
The sky still threatens wind and rain!
I'm sure Anniemay will let me know if this will pass for today's topic "Perpendicular" she just can't let go of the mathematical equations, once a math teacher always a math teacher! Bless :-)