“About some events related to the hail origin”

Angelo Secchi
Atti dell’Accademia Pontificia dei Nuovi Lincei, vol. 29 (1876), 1-7
305 x 225 mm
Biblioteca Storica centrale della Meteorologia Italiana, CREA-AA, Roma

Among his many meteorology researches, Father Secchi undertook to study the mechanisms of the formation of the hail and in 1875 formulated a rational and well-concordant scientific hypothesis with the explanation of congeners meteorological phenomena , which for the first times involves the laws of dynamics and thermodynamics of the atmosphere. These researches were presented by Secchi to the Pontifical Academy of the New Lynceans, in the session of 19 December 1875.
The news of the sudden and very violent “aerial vortex” met by Rosalie Gujon widow Poitevin, aviation pioneer, and other fellows, at 1200 m a.s.l. during an ascension in balloon executed from Rome in 1867 would be among the causes which inspired Secchi for the study of the mechanisms of formation of the hail. Secchi observed the ascension with the Merz telescope and noticed the vortex, which suddenly dropped the balloon, forcing the crew to gather in the cage of the ballon. They then reported that the cold air inside that vortex had been so intense that “in less than five minutes the water bowl brought by them was frozen.”
Secchi thus indicates various factors that act in the formation of hail, in particular the whirling air movement and the cooling of these masses in the upper atmosphere. This idea is also found in the studies of Hervé Faye, who in those years had formulated a theory about the formation of hail; unlike Faye, however, on the basis of his observations, Secchi believed that the vortices formed in the lower atmosphere.
The approach to understanding the origin of hail proposed by Father Secchi constitutes an important attempt to theorising the phenomenon, even if, to date, the exact mechanism of its formation has not yet been completely clarified.

Maria Carmen Beltrano, CREA-AA

F. Denza, “Meteorologia e fisica del globo” (cap. IX e X), Annuario scientifico ed industriale, anno XIII (1876), 138-152;
I. Galli, La teoria del p. Secchi sull'origine della grandine, esposta e paragonata coi fatti dall'ab. Ignazio Galli, direttore del l'osservatorio di Velletri ecc. (Velletri: Regia tipografia di Angelo Sartori, 1876).