Horton-Smith, a scholar of early Italic languages and a contributor to A Grammar of Oscan and Umbrian, presents a defense of the Law of Thurneysen and Havet. This law states that in the course of the third century B. C. among the upper classes (but not before the beginning of the second century B. C. among the lower classes), in consequence of very open pronunciation of o before u three changes occurred. First, Prim. Lat. ov- (preserving Idg. o) av-, second Prim. Lat. ov- (preserving Idg. o), av-, and finally the Prim. Lat. diphthong ou from Idg. tautosyllabic ou became the diphthong au on its way to the later u/ o. The essay presents a variety of literary evidence for this position, and indeed Horton-Smith's opinion still informs our understanding of Latin of the early Republic. Classicists and linguists will find this helpful and interesting to their understanding of Latin's development during the crucial period of increased contact with the Greek East.