This one was close (in time). Really it is my fault for having both twitter submissions and comment submissions. However, I am pretty sure the first answer came from Dale Basler (from Lab Out Loud). Here is his post:
And yes, that is correct. Here is an image from my giant Cenco catalog.
And the description:
Yes, I know I don't have the needle. That just makes it more challenging. But basically, this is the same as another What the heck is this post - the ampere's law apparatus.
