The River Frome, which is beyond the fence to the right in the top photo, passes under the canal at this point. The red brick wall is one end of the aqueduct. The other end of the aqueduct is marked by the railings, and is the subject of the second photo. Note there is no air gap between the water and the top of the culvert.
This is a 'syphon' aqueduct which consists of two stone arch culverts under the canal bed, and is easy to miss when walking the towpath. This is just past the end of the new Capel's Mill section of canal.
(Tap / click images to enlarge)