Thanks to a tip off from Dave at work I've found more on Farnham Whitebines and the unresolved mysteries of the Mathon.
On the
Willingham Nurseries website is a PDF of the 1905 book
The Hop and its Constituents by A C Chapman. To my delight it includes a couple of chapters by John Percival, author of the famous article from 1901
The Hop and its English Varieties. Once again he provides details of English hop varieties, but slightly annoyingly in the intervening four years he seems to have become less convinced that the Canterbuy, Farnham and Mathon Whitebines are exactly the same plant. Though to cloud the issue further being grown in different areas and probably harvested at different times would account for some variation.
Here's what he had to say on this fascinating conundrum:
'The main crop sorts cultivated in the best hop-growing districts are the Canterbury, Farnham and Mathon varieties, with the true Golding hop. These are similar to each other in many respects, and in all probability are genetically related. The Canterbury, Farnham and Mathon hops all have pale green or "white" bines, which grow to a great height if allowed.
The Canterbury whitebine is largely grown in East Kent, the Farnham hop around the town of this name in Surrey, while the Mathon is the Worcestershire and Herefordshire representative of this class.
The cones are of medium size, oval in shape, those of the Farnham hop being the least of the trio, the Mathon perhaps the largest, although there is not much difference in size. All have thin pale golden petals, rich in lupulin, and the flavour and aroma are all that is desired.
On account of their delicate constitution they cannot be grown profitably except in the favoured districts where soil and climate are suitable.
The Cobbs' Hop is a main crop variety of recent introduction. It is hardier than the Canterbury type with thin pale petals.It is an excellent cropper where the climate and land are satisfactory, but is generally not rich in lupulin.
The "Golding" Hop resembles the Canterbury and Farnham types. It is often confused with these, and gardens supposed to be pure usually contain both Goldings and Canterbury Whitebines.
The true Golding hop has slightly larger cones not so clustered together as the Canterbury sort, and the bine is not so tall and is more speckled with red blotches and streaks.'