[18] On Ronalds' work see reports of the British Association for the Advancement of Science, from 1846 to 1850. On Brooke's work see _Philosophical Transactions of the Royal Society of London_, 1847, vol. 137, pp. 59-68. [19] C. Abbe, "The Meteorological Work of the U.S. Signal Service, 1870 to 1871," in Fassig, _op. cit._ (footnote 12), pt. 2, 1895, p. 263. [20] _Annual Report of the Director of the Meteorological Observatory_, Central Park, New York, 1871, p. 1ff. [21] _Oesterreichische Gesellschaft für Meteorologie, Zeitschrift_, 1871, vol. 6, pp. 104, 117. [22] P. H. Carl, _Repertorium für physikalische Technik_, Munich, 1867, p. 162ff. [23] E. Lacroix, _Études sur l'Exposition de 1867_, Paris, 1867, vol. 2, p. 313ff. See also, Reports of the U.S. Commissioners to the Paris Universal Exposition, 1867, vol. 3, Washington, 1870, p. 570ff. [24] _Annals of the Dudley Observatory_, 1871, vol. 2, p. vii ff. [25] Karl Kreil, _Entwurf eines meteorologischen Beobachtungs-Systems für die österreichische Monarchie_, Vienna, 1850. [26] _Report of the 13th Meeting of the British Association for the Advancement of Science_, 1843, 1844, p. xi ff. I have found no other reference to this instrument. Considerable attention was given to the thermometer, however, for Wheatstone proposed to send it aloft in a balloon for the measurement of temperatures at high altitudes. A small clock caused a vertical rack to ascend and descend once in six minutes. The rack carried a platinum wire which moved within the thermometer over 28 degrees. From a galvanic battery and a galvanometer on the ground two insulated copper wires were to extend to the balloon, one connected to the mercury and the other to the clock frame. The deflection of the galvanometer was to be timed with a second clock on the ground. (Professor Wheatstone, "Report on the Electro-Magnetic Meteorological Register," _Mechanics' Magazine_, London, 1843, vol. 39, p. 204). [27] In 1662 Hooke had proposed the use of a bimetallic pendulum for the temperature compensation of clocks. Thermometers on this principle were described to the Royal Society in 1748 and in 1760 (_Philosophical Transactions of the Royal Society of London_, 1748, vol. 45, p. 128; 1760, vol. 51, p. 823). Some systems used a bimetallic thermometer in the sun and a mercurial instrument in the shade.