Mechanisms of the Meteorographer-the Thermometrographer

"Descrizione del Meteorografo dell’Osservatorio del Collegio Romano"
Angelo Secchi
Bullettino Meteorologico dell’Osservatorio del Collegio Romano, vol. V, 1866
Tavola III
Engraving, 300x215mm
Biblioteca centrale della Meteorologia Italiana-CREA-AA, Roma

The apparatus of measurement of the temperature chosen by Secchi for the meteorographer was “the metallic Kreil thermometrograph installed in Vienna and also in Kremsmünster very successfully. The provision of the observatory was such that we could erect it almost in the same circumstances, […] and perhaps even more favourable. ”
The apparatus consisted of a copper wire 17 metres long, 5.5 mm in diameter, suspended vertically along the northern wall of the eastern arm of the Church of St. Ignatius, whose central body still remained “distant more than 10 m [from the wire], in order to never confine the mass of air at all”,” attached at the bottom to a strong iron modillion 53 cm long, which keeps him detached from the wall. ” “To the east is all free and therefore subject to the morning sun. To avoid this inconvenience it was made to put a curtain of canvas of sails. ”
On the basis of the descriptive sketch of the apparatus, depicted in the table shown here, in Fig. 11, a few years ago I searched for the traces of the installation along the north face of the eastern arm of the church, adjacent to the seat of my office, and it was a great emotion to have identified and recognized, spared by time and man, the modillion providing anchorage to the copper wire, the system of cables that supported the canvas of protection sails and, in the cornice of the church, the holes through which the thread of the sensor and the sail supports passed (figures 1-2).
The thermometric apparatus was complemented by a superior horizontal portion of 8-metre long iron wire protected “by a wooden roof”, connected to the copper one by a spliced mobile square in the cornice, and by a system which kept the wires tensioned. The whole mechanism allowed the propagation of the movement of the copper wire up to the lever connected to the “lapis” which traced the curve on the chart paper of the meteorograph.

Maria Carmen Beltrano, CREA-AA

Bibliography
A. Secchi, “Descrizione del Meteorografo dell’Osservatorio del Collegio Romano”, Bullettino Meteorologico dell’Osservatorio del Collegio Romano, numero 4 vol. V, 30 aprile 1866, pp. 25-44;
“La météorologie et le météorographe à l’exposition universelle”. Extrait des études religieuses, historiques et littéraires par des pères de la Compagnie de Jésus (Paris: Gauthier-Villars, 1867).