Burnt Wire

So, I just made a new positive battery cable going to the starter. (1970 duster slant 6) When I got in and turned the key, nothing happened. Then this wire (picture) burnt all the way through. Form what I can see, this does nothing and it is a ground to itself. If anyone has any explanation on what this wire does or why it burnt it would be greatly appreciated. (wire was white)IMG_20210218_143424.jpg IMG_20210218_143427.jpg