"It was quite different in its character from the _Diatessaron_ of
Tatian. The _Diatessaron_ of Tatian was a patchwork of the four
Gospels, commencing with the preface of St. John. The work of
Ammonius took the Gospel of St. Matthew as its standard, preserving
its continuity, and placed side by side with it parallel passages
from the other Gospels. The principle of the one was _amalgamation_;
of the other, _comparison_. No one who had seen the two works could
confuse them, though they bore the same name, _Diatessaron_.
Eusebius keeps them quite distinct. So does Bar-Salibi. Later on in
his commentary, we are told, he quotes both works in the same
place." [148:2]

Doubtless, no one comparing the two works here described could confuse
them, but it is far from being so clear that anyone who had not seen
more than one of these works could with equal certainty distinguish it.
The statement of Dr. Lightfoot quoted above, that the _Diatessaron_ of
Ammonius "took the Gospel of St. Matthew as its standard, preserving its
continuity," certainly does not tend to show that it was "quite
different in its character from the _Diatessaron_ of Tatian," on the
supposition that the Arabic translation lately published represents the
work of Tatian. I will quote what Professor Hemphill says regarding it,
in preference to making any statement of my own:--

"On examining the _Diatessaron_ as translated into Latin from this
Arabic, we find in by far the greater portion of it, from the Sermon
on the Mount to the Last Supper (§§ 30-134) that Tatian, like his
brother harmonist Ammonius, took St. Matthew as the basis of his
work ... St. Mark, as might be expected, runs parallel with St.
Matthew in the _Diatessaron_, and is in a few cases the source out