Hessel, Johann Friedrich Christian

(b. Nuremberg, Germany, 27 April 1796; d. Marburg, Germany, 3 June 1872), mineralogy,

crystallorgraphy.

Hessel’s most important scientific contribution was his mathematical derivation, from consideration of the symmetry elements of crystals, of the fact that there can be only thirty-two crystal classes and that only two-, three-, four-, and sixfold axes of symmetry can occur. His results, published two decades before the work of Bravais, were overlooked until Leonard Sohncke drew attention to their importance in 1891.

After attending the industrial school (later the Realschule) at Nuremberg, Hessel studied science and medicine at Erlangen and Würzburg, from which he received the M.D. in 1817. He pursued further scientific studies at Munich, where he met the noted mineralogist Karl C. von Leonhard, who persuaded Hessel to accompany him as his assistant to Heidelberg. There, Hessel studied physics, chemistry, mathematics, and, in particular, mineralogy and crystallography. He received the Ph.D. in January 1821 and was called to Marburg that fall as associate professor of mineralogy and mining technology. He became full professor in 1825 and remained at Marburg until his death.

In addition to his teaching, Hessel was active in the administration of the university and served for five years as a member of the Marburg city council. He published over forty scientific books and articles, primarily in mineralogy and crystallography but also in physics, astronomy, chemistry, zoology, and botany. In 1826 Hessel demonstrated that the family of plagioclase feldspars could be considered as an isomorphous series consisting of albite and anorthite combined in all proportions, and he suggested a chemical formula for these feldspars. His results, presented in an article entitled “Ueber die Familie Feldspath” (Taschenbuch für die gesammte Mineralogie, 20 [1826], 289–333), did not receive contemporary attention; and this theory of the composition of the feldspars became prominent only with the work of Gustav Tschermak in 1865.

Hessel’s statement of the possibility of only thirtytwo crystal classes was obtained from an exhaustive analysis of the possible types of symmetry which any geometrical form might present. From a mathematical point of view, the later work of Bravais was more elegant. Hessel’s results initially appeared in 1830, in an article entitled “Krystall” in Gehler’s physikalisches Wörterbuch; and although the article was published separately in the following year, Hessel’s work received no recognition among his contemporaries.

BIBLIOGRAPHY

I. Original Works. Hessel’s books include Ueber Positive und negative Permutationen (Marburg, 1824); Einfluss des organischen Körpers auf den anorganischen, nachgewiesen an Encriniten, Pentacriniten, und anderen Thierversteinerungen (Marburg, 1826); Krystallometrie, oder Krystallonomie und Krystallographie, besonders abgedruckt aus Gehler’s physikalischem Wörterbuche (Leipzig, 1831), new ed., edited by E. Hess (Leipzig, 1897). Ostwald’s Klassiker der Exakten Wissenschaften, nos. 88 and 89; Versuche über Magner-Ketten and über die Eigenschaften der Glieder derselben, besonders über jene, welche ihnen angewöhnt oder auf sonstige Weise willkürlich ertheilt werden Können (Marburg, 1844); Löthrohrtabellen fürmineralogische und chemische Zwecke (Marburg, 1847); Die Anzahl der Parallelstellungen und jene Coincidenzstellungen eines jeden denkbaren Raumdinges mit seinem Ebenbilde und mit seinem Gegenbilde, der Regelmässigkeitsgrad der Schwerpunctes und andere bei Raumdingen in Betracht kommende Zahlen, als Merkmale für den Begriff Familie von Raumdingen nachgewiesen (Kassel, 1853); Die Weinveredelungsmethod des Altertums verglichen mit denen der heutigen Zeit (Marburg, 1856); Die merkwürdigen arithmetischen Eigenschaften der wichtigsten Näherungsreich für die Sonnenabstände der Planeten (Marburg, 1859); and Uebersicht der gleicheckigen Polyeder und Hinweisung auf die Beziehungen dieser Körper den gleichflächigen Polyedrn (Marburg, 1871).

II. Secondary Literature. See the following, listed chronologically: Leonard Sohncke, “Die Entdeckung des Eintheilungsprincips der Krystalle durch J. F. C. Hessel,” in Zeitschrift für Krystallographie, 18 (1891), 486–498; Edmund Hess, “J. F. C. Hessel: Zur Säcularfeier seines Geburtstag,” in Neues Jahrbuch für Mineralogie, 2 (1896), 107–122. For annotations on Hessel’s work, see Hess’s ed. of Krystallometrie mentioned above (esp. no. 88).

John G. Burke