[1] A minute knowledge of printed books and a methodical examination of departmental and communal archives furnished him with material for a long course of successful lectures, which gave rise to some important works on municipal history and led to a great revival of interest in the origins and significance of the urban communities in France.

[1] About this time personal considerations induced Giry to devote the greater part of his activity to the study of diplomatics, which had been much neglected at the École des Chartes, but had made great strides in Germany.

In 1894 he published his Manuel de diplomatique, a monument of lucid and well arranged erudition, which contained the fruits of his long experience of archives, original documents and textual criticism; and his pupils, especially those at the École des Hautes Études, soon caught his enthusiasm.

[1] In the midst of these multifarious labours Giry found time for extensive archaeological researches, and made a special study of the medieval treatises dealing with the technical processes employed in the arts and industries.

He prepared a new edition of the monk Theophilus' celebrated treatise, Diversarum artium schedula, and for several years devoted his Saturday mornings to laboratory research with the chemist Aimé Girard at the Conservatoire des Arts et Métiers, the results of which were utilized by Marcellin Berthelot in the first volume (1894) of his Chimie au moyen âge.