In 1853 Johann Caspar Zeuss, from Oberfranken in the kingdom of Bavaria, published in Latin a work of 1163 pages entitled Grammatica Celtica; in 1913 a Danish linguist, Holger Pedersen, completed the second and final volume of his Vergleichende Grammatik der keltischen Sprachen. These two books were the beginning and the end of the period in which Celtic linguistic scholarship flourished most vigorously outside the Celtic– or recently Celtic–speaking countries; they form the end–points of my essay. About the principal scholars of the period I shall ask two questions: what drew them to work on Celtic and what, more importantly, kept them working in this field even after, very often, their initial concerns had been satisfied.

Celtic came late and hesitantly to the philological feast. In the decade after the Battle of Waterloo the discipline of Indo–European comparative philology was established on the lines which would, with appropriate development, be followed until the present day. The crucial argument was that comparison between languages could lead to proof that they were genetically related provided that, first, isolated comparisons between words were avoided and, secondly, attention was focused on some of the central and relatively conservative parts of a language, such as its pronouns or numerals or kinship terms. If systematic equivalences could be demonstrated in such areas, such as that between English f and th as against Latin p and t in, say, father: pater, then one had secure evidence on which to posit that both descended from a third language. A further crucial weapon in the armoury was to distinguish between inherited elements of the language and borrowings from one language into another; for example, fame in English does not have a Latin counterpart beginning with p; instead it is derived, via French, from Latin fama. To confirm equivalences of the father: pater type, one had to exclude the quite different relationship seen in fame and fama. Three steps then led to Indo– European, namely to the positing of a language which had once existed in remote prehistory, but which had split up into numerous daughter– languages, just as Latin gave rise not just to Italian but to French, Spanish and the other Romance languages.