The Genius of Language: Observations for Teachers. A set of six lectures given to the faculty of the Waldorf School in Stuttgart, Germany from December 26, 1919 to January 3, 1920. (CW 299)
For your convenience, below is a zip file of this entire set of lectures. It does require that you have an unzipping utility of some kind on your computer. For you mac people this is built in.
The Entire Book The Genius of Language: Observations for Teachers
1. Language from an Historical Standpoint
2. The Evolution of Language from an Organic Point of View
3. The Transforming Powers of Language in Relation to Spiritual Life
4. History of Language in Its Relation to the Folk Souls