As illustrating the character of the encyclopedias it is worth while to notice more fully the method by which they were produced. As has been suggested, Roman scholars and scientists under the Empire were little more than note-takers. Pliny the Elder is the typical example of this tendency; a student of extraordinary diligence, his study consisted in reading, making extracts, and compiling them. Such was the origin of his _Natural History_. He left to his nephew, in addition, the legacy of “one hundred and sixty common-place books, written on both sides of the scroll and in very small hand-writing”.[47] The full effect of the tendency thus illustrated cannot be perceived, however, if we think merely of the process as it was carried on by Pliny, for he consulted chiefly original works; when, later, extracts began to be made from works that were themselves compiled from extracts, when epitomes began to be epitomized, a state of confusion and feebleness of thought inevitably ensued. This is the condition which is exemplified in the two latest of the Roman encyclopedists, Pompeius Festus and Nonius Marcellus, and the tradition is continued in Isidore. [47] Younger Pliny, _Epistles_, 3, 5. The body of knowledge gathered together under all these influences possessed little of a positive nature. It was informed by no general ideas of a striking character and it entirely lacked the element of reasoned proof. Since its science was a science of authority, it was easy for the Christian writers to modify it by substituting the authority of the Scriptures for that of pagan writers. In fact, the encyclopedias furnished to the church fathers secular knowledge in a particularly convenient and unobjectionable form. Augustine, especially, made great use of Varro. It can be seen that this literary form was better adapted than any other to pass with unbroken continuity from ancient into medieval literature. It is then to the succession of Roman encyclopedists that we must go to explain the method, spirit, and content of Isidore’s _Etymologies_. A comparison of the organization of the material and of the sub-titles of Isidore’s work with those of the Roman writers,[48] so far as they are known, shows the extent of his indebtedness. The literary and philological flavor, the stress on word history and derivation, the pseudo-science based on authority, the conspicuous tendency to confusion and feebleness of thought, the habit of heedless copying that we find in an aggravated form in the _Etymologies_, all these are inherited characteristics that betray the origin of the work. [48] An outline of the contents of leading encyclopædic works, so far as known, is here given for purposes of comparison with the contents of the _Etymologies_.