Thanks Kacy !
Actually, the "disagreement" was between Snell and Clark
.
Clark had taken over Shelley's position as a teacher at the "Hand and Pen" in Warwick Lane when Shelley was appointed master at Christ's Hospital, in 1710. Christ's Hospital was an enviable position, and Snell seems to have been a little envious... He expressed what he thought of Shelley's work and Clark defended Shelley (who was not as outspoken and confident as Clark was).
The argument kept going between Clark and Snell :
Snell criticized the what he saw as a lack of precision in the explanations on writing published by Clark in Writing Improv'd. In my opinion (from reading the details of the argument published both in books and newspapers), Snell was just a man of bad faith, jealous that Clark managed to publish his own rules before he could, and unable to admit that other masters could have contributed to the development of the RH as much as he did... He liked to say he was the first to publish things.
Clark defended himself with some reason, the argument was made public through publications in newspapers until 1717... Which, some thought, completely discredited the profession in the eyes of the public. In the end, what I retained from this is that Clark allowed more variety / fancy in his writing than Snell did. Snell wanted to work according to very strict rules, which were probably not very practical for a handwriting system. He was probably too much of a perfectionist. He was very talented, but this may have made him a bit of a snob.
Years later, Bickham engraved a plate representing the "fathers" of the RH. He placed Clark at the top and Snell at the bottom... Not that is opinion is unbiased... He engraved all the copybooks of these masters from 1709 to his / their death. He confessed that Clark had been the first to instruct him in the art of writing, and had done a superb job. But he also had great admiration for Snell's most famous pupil : Joseph Champion. (See the plate I'm referring to here :
https://www.britishmuseum.org/research/collection_online/collection_object_details/collection_image_gallery.aspx?partid=1&assetid=164997001&objectid=1506724#more-views