A.C. Clark produced two important works on NT TC, the first being The Primitive Text of the Gospels and Acts (Oxford, 1914), and the second, his Critical Text of Acts (1933). Although his continued investigation resulted in modifications and additional details, his basic position remained committed.
Here are some exerpts from the first book (Primitive Text..):
...Whenever the readings of two MSS ...are compared, ...one of them does not contain passages which occur in the other. In all such cases there are two possible explanations, viz., that the words are spurious, ...inserted by an interpolater..., or that they are genuine, and have been accidentally omitted by the other [copy]. The hypothesis of accident [omission] is highly probable, when there is a reason which will account for the omission.One such reason is universally recognized, viz., homoeoteleuton. [h.t.] When a similar ending, or word occurs twice in the same sentence, a copyist [could have] easily passed from the first passage to the second, omitting the intermediate words. This saut du meme au meme ["jump from meme to meme"] is the most prolific cause of omissions.There is another reason which is not infrequently suggested by editors, viz., that the scribe has accidentally omitted a line, or several lines, of his model. When we have two MSS, one which is known to be a transcript of the other, we find actual instances of such omissions. In the vast majority of cases however, we have only the copy, not the [exemplar]. Since all scribes [copyists] are subject to the same errors, it is reasonable to suppose that omissions in a particular MS may represent a line or number of lines [skipped] in an ancestor... the problem is to find an objective criterion..to detect line-omissions....[groups of] short passages...doubted on the ground of their omission by a MS or family, frequently contain the same, or nearly the same number of letters. Longer passages in the same way [are] multiples of this unit. The natural inference is that the unit [and longer omissions] correspond to [physical] lines in [the layout of] an ancestor.Ancient Uncial MSS are written with few abbreviations and no space between words [with] the number of letters per line ...a more or less constant [average] quantity.It was also easy for a copyist to omit other divisions in his [exemplar], viz., a colum, page, or folio [folded sheet]. Since it is usual for MSS to have the same # of lines per page, it follows that the contents of columns, pages, & folios are similar [in size]....The chief result of my investigation has been to show the falsity of the principle brevior lectio potior ("prefer the shorter reading"). This was laid down by Griesbach as a canon of criticism in the words:"Brevior lectio, nisi testium vetustorum et gravium auctoritate penitus destituatur, praeferenda est verbosiori. Librari enim multo proniores ad addendum fuerunt quam ad omittendum.""The Shorter reading, unless the authority of the witnesses completely lacks a weight and age, is preferable to the verbose. Copyists were much more prone to add than to omit."
[But] this statement has no foundation in facts. I may also observe that it is not so easy to invent as it is to omit.
I had been brought up to look on the Revised Text as final, to smile at persons who maintained the authenticity of St. Mark 16:9-20 or St. John 7:53-8:11, and to suppose that the 'vagaries' of the 'Western text' were due to wholesale interpolation. The object which I had in view was merely to study the mutual relations of the oldest Greek Uncials, notably, the Vaticanus (B), Sinaiticus (Aleph), and Alexandrinus (A). I was however, soon dislodged from this arrogant attitude, and irresistibly driven to very different conclusions.
Nowhere is the falsity of the maxim 'Prefer the shorter reading' more evident than in the New Testament. The process [over time in copying] has been one of contraction, not expansion. The primitive text is the longest, not the shortest."
(- Clark, 1914, Preface, iii-vii)