Unfortunately the stamp has been removed (or fallen off). The envelope appears to be from Exeter but the address on the envelope could be either North or South Petherton.
The post office decided to try North Petherton first and sent it via Bridgwater, North Petherton's post town, on 22nd July 1849. Major Kingdon was not known at North Petherton (manuscript "Not Known at North Petherton" in red), going back via Bridgwater where it received a faint blue-grey "BRIDGEWATER / 8" skeleton cancel dated 23rd July 1849.
The post office then tried South Petherton, going via Ilminster, South Petherton's post town. Major Kingdon was not known there (manuscript "Unknown at" with South Petherton double arc handstamp dated 25th July) and the envelope then appears to have gone back to Bridgwater where it received a "BRIDGWATER / 5" skeleton cancel on 6th August 1849.
The Bridgwater handstamps on the reverse of the envelope are very hard to distinguish; here is an image of the reverse of the envelope, the first Bridgwater handstamp being below the Exeter handstamp, the second, skeleton handstamp having the "8" by the final "E" of "EXETER", and the third, skeleton handstamp being overlaid by the Exeter mark.
Here is a larger image of the "BRIDGWATER / 8" skeleton, with a date of 23rd July 1849. The "8" is by the final "E" of the Exeter handstamp.
Here is a larger image of the "BRIDGWATER / 5" skeleton, showing a date of 6th August 1849.
On 8th August 1849 a "recut" "BRIDGEWATER" double-arc dated handstamp was registered in the Steel Impressions Book, marking the likely end of use of the skeleton.