According to the internet, which is supposedly never wrong, the original Rumbling Bridge was built in 1713 by William Gray, carrying a road across the River Devon, at a point where it drops deep into a gorge, the water's rumbling sound giving the bridge its name. It's a masonry arch spanning about 7m, and without any parapets.
Again according to the internet, the second arch bridge was built above the original in 1816, leading to an unusual double arch bridge which is well worth seeing, particularly above the somewhat spectacular river gorge.
Quite how accurate or complete the internet's information is must be open to doubt, as there's a stone clearly visible on the bridge inscribed with the name "T.H. Tuckett" and dated 1664, which suggests there was a bridge on this site at an earlier date.
The photo at the start of this post is a panorama and hence slightly distorted and doesn't really give a good idea of the depth from the top of the bridge to the river below - it's deeper than it looks (36m). The old postcard on the left gives a slightly better idea and shows that at one time it was possible to walk across the lower arch - it's a real shame that's no longer an option.
It's unclear precisely why the lower arch bridge was left in place, as it must have been rendered largely unuseable during erection of the timber centering for the upper arch, and remains unuseable now. I did wonder briefly whether it formed some propping function, but that also seems unlikely.
Whatever, it's an unusual and picturesque bridge, worth the short detour from our journey.