Page "Comparative method" Paragraph 2

The comparative method was developed over the 19th century.

Key contributions were made by the Danish scholars Rasmus Rask and Karl Verner and the German scholar Jacob Grimm.

The first linguist to offer reconstructed forms from a proto-language was August Schleicher, in his Compendium der vergleichenden Grammatik der indogermanischen Sprachen, originally published in 1861.

Here is Schleicher ’ s explanation of why he offered reconstructed forms: