thirteen and a quarter miles, where the barometric pressure was reduced to one and a half inches of mercury. (In Plate I. this extreme and possibly excessive height is not shown as the height of the _ballon-sonde_, but the average of the three highest ascents of the _Cirrus_ is indicated.) The comparative warmth (-50∞ Fahrenheit) recorded has led Dr. Assmann himself to doubt the accuracy of the usual methods of registering temperature at such extremely low pressures. Plate VII. shows the heights in metres, and the temperatures in degrees Centigrade, during eight voyages from Berlin prior to June 1897. Notwithstanding the rivalry and difference of opinion between the Germans and French as to the methods of exploring the high atmosphere, there was also a sincere desire to co-operate, and the International Meteorological Conference which was held at Paris in September 1896 furnished an opportunity to make the arrangements. Resolutions were adopted favouring ascents with manned balloons, as well as simultaneous ascents of _ballons-sondes_ in the different countries. The successful use of kites at Blue Hill to lift self-recording instruments more than a mile into the air led to the wish that similar experiments should be tried elsewhere. An International Committee was appointed to carry out these resolutions, of which Professor Hergesell of Strassburg is president, and the veteran Parisian aeronaut and journalist, Wilfrid de Fonvielle, is secretary. [Illustration: PLATE VII.--HEIGHTS AND TEMPERATURES RECORDED IN EIGHT ASCENTS OF THE _CIRRUS_.] It was agreed to make a night ascent and to use identical instruments, in order that the observations might be made everywhere under the same conditions. Accordingly, on the early morning of November 14, 1896, five balloons manned by observers, and three _ballons-sondes_ with recording instruments, were liberated in France, Germany, and Russia. By means of the automatic diagrams from the _ballons-sondes_, and the direct observations in the manned balloons, it was sought to determine the decrease of temperature with height in vertical sections of the atmosphere connecting the various centres from which the balloons started. Seven such sections were available by connecting Paris and Strassburg, Berlin and St. Petersburg, Warsaw and Munich, etc., but, unfortunately, observations in the highest strata were generally lacking.