Aeroklinoscope, an instrument recently introduced on the continent of Europe, in connection with the weather signal departments. It is intended to give public information of the condition or rather differences of barometric pressure at the different stations, so that every one at a glance may see in what quarter the maximum and minimum barometric pressure is, and consequently what direction of wind and what kind of weather are to be expected. The apparatus as now in practical use consists of a vertical axis some 30 feet high, turning on a pivot, and carrying on its top a horizontal arm of which the inclination can be varied accord-in?; to the difference of barometrical pressure at different sides of the station. If the pressure is the same north an south, for instance, the horizontal arm is placed horizontal; but if the pressure is less in the nortn, the northern end of the arm is caused to dip downward, and more so in proportion as the barometer is lower north as compared with its position south. The amount of dip is regulated by a sliding rod, held in position by different notches at the lower part of the axis, each notch corresponding with one millimetre in barometric pressure.

This most useful apparatus is the invention of Buys-Ballot in Holland.

The government of the Netherlands introduced storm signals there in 1860; England followed in 1861, and France in 1863.