Eugene Howard Babbitt in his 1896 publication on The English pronunciation of the lower classes in New York and vicinity mentions the usage of the glottal stop in the New York accent on p. 8:
Jespersen in his book Fonetik of 1897-1899 makes this comment on p. 299:
Joseph Wright in his 1905 English Dialect Grammar briefly mentions the fact that in some Scottish dialect areas intervocalic /t/ is replaced by the glottal catch:
In his Modern English grammar, vol. 1 (1909), Otto Jespersen writes this:
In 1913 William Grant publishes his Pronunciation of English in Scotland. On p. 30 we find this observation:
Not only are glottal reinforcement and replacement to be heard in connection with /p, t, k/ but also with /n, ŋ/.
I wonder if Dobson has anything to say on this topic in his monumental English pronunciation.