Consider the premise. Does the hypothesis stand independently without contradicting or following it? Premise: The total was approximately 2800, but that is probably only a vague  he undoubtedly missed some; some have sprung up since his time (modern Hebrew, for instance); and some have vanished. Hypothesis: He was overworked. 
The total was approximately 2800, but that is probably only a vague  he undoubtedly missed some; some have sprung up since his time (modern Hebrew, for instance); and some have vanished.###He was overworked. 