A crucial stopping-point on the road to the early understanding of the Avestan language, Spiegel’s work was an early European attempt to comprehend this ancient and complex language. One of the two oldest languages of Iran, Avestan is probably best known as the language of the Zoroastrian Avesta. This historic grammar of the language has an extensive introduction to the writing system, the phonetics of the language and the rules of how the sounds are pronounced. He discusses the way words are constructed and inflection before moving on to a considerable discussion of syntax. There is also an appendix on the Gatha dialect of the language.