See Sir H. Chauncy, _Historical Antiquities of Hertfordshire_ (London, 1700, 2nd ed., Bishop Stortford, 1826); N. Salmon, _History of Hertfordshire_ (London, 1728); R. Clutterbuck, _History and Antiquities of the County of Hertford_ (London, 1815-1827); W. Berry, _Pedigrees of the Hertfordshire Families_ (London, 1844); J. E. Cussans, _History of Hertfordshire_ (London, 1870-1881); _Victoria County History, Hertfordshire_ (London, 1902, &c.); see also "Visitation of Hertfordshire, 1572-1634," in _Harleian Society's Publ._ vol. xvii., and various papers in _Middlesex and Hertfordshire Notes and Queries_ (1895-1898), which in January 1899 was incorporated in the _Home Counties_ Magazine. HERTHA, or NERTHUS, in Teutonic mythology, the goddess of fertility, "Mother Earth." Tacitus states that many Teutonic tribes worshipped her with orgies and mysterious rites celebrated at night. The chief seat of her cult was an island which has not been identified. A single priest performed the service. Her veiled statue was moved from place to place by sacred cows on which none but the priest might lay hands. At the conclusion of the rites the image, its vestments and its vehicle were bathed in a lake. HERTZ, HEINRICH RUDOLF (1857-1894), German physicist, was born at Hamburg on the 22nd of February 1857. On leaving school he determined to adopt the profession of engineering, and in the pursuance of this decision went to study in Munich in 1877. But soon coming to the conclusion that engineering was not his vocation he abandoned it in favour of physical science, and in October 1878 began to attend the lectures of G. R. Kirchhoff and H. von Helmholtz at Berlin. In preparation for these he spent the winter of 1877-1878 in reading up original treatises like those of Laplace and Lagrange on mathematics and mechanics, and in attending courses on practical physics under P. G. von Jolly and J. F. W. von Bezold; the consequence was that within a few days of his arrival in Berlin in October 1878 he was able to plunge into original research on a problem of electric inertia. For the best solution a prize was offered by the philosophical faculty of the University, and this he succeeded in winning with the paper which was published in 1880 on the "Kinetic Energy of Electricity in Motion." His next investigation, on "Induction in Rotating Spheres," he offered in 1880 as his dissertation for his doctor's degree, which he obtained with the rare distinction of _summa cum laude_. Later in the same year he became assistant to Helmholtz in the physical laboratory of the Berlin Institute. During the three years he held this position he carried out researches on the contact of elastic solids, hardness, evaporation and the electric discharge in gases, the last earning him the special commendation of Helmholtz. In 1883 he went to Kiel, becoming _Privatdozent_, and there he began the studies in Maxwell's