METEOROLOGY AND ALLIED SUBJECTS. 251 



air-box in its metallic case and insert within it tlie two glass tnbes con- 

 nected with the drying apparatus and the manometer, respectively. By 

 suction the air within the chamber is withdrawn and replaced by fresh 

 air from the place of observation. After reading the barometer, the air 

 within the chamber is dried hy sulphuric acid, after which the baromet- 

 ric pressure within the chamber is again determined. The results of 

 this simple and convenient apparatus are absolutely correct and reli- 

 able, as has been shown by many series of experiments, and as also 

 appears from the entire arrangement of the apparatus and the principle 

 adopted in it. This apparatus serves for independent, accurate hygro- 

 metric observations, and the verification of the results given by psy- 

 chrometers and other less reliable instruments. {Z. 0. G. M., XIV, 

 1879, p. 56.) 



The patent hygrometer by Professor Kliukerfues has been studied by 

 Dr. Mlittrich. This instrument consists of two hygroscopic threads, or 

 hairs, a thermometer to determine the temperature of the air, and a 

 disk for determining the dew-point. Miittrich finds that large errors 

 in the relative humidity occur during various portions of the same day, 

 and the instrument does not correspond to the requirements of meteor- 

 ology. {Z. 0. G. M., Vol. XV, 1880, p. 170.) 



Rudorlf has made a comparative study of the methods of determining 

 the aqueous vapor present in the atmosphere. The Schwackhofer ap- 

 paratus, on account of its high price and complication, seems to be less 

 desirable than that devised by Edelmann, in which from a given quan- 

 tity of air the aqueous vapor is absorbed by sulphuric acid, and the 

 dimiuution of atmospheric pressure is measured by meaus of a manometer. 

 But a still simpler apparatus is that devised by Eudorff himself. In 

 this a given quantity of air is inclosed in a given chamber ; the aqueous 

 vapor is then absorbed from the air, and consequently the pressure in 

 the chamber is tUminished. This change in pressure can now be coun- 

 teracted bj^ the gradual addition of sulphuric acid until the original 

 pressure is reproduced, and the absorbed aqueous vapor is thus re- 

 placed by an equal amount of sulphuric acid, which volume can, of 

 course, be easily measured. The apparatus allows of the determination 

 of the volume of weight of the aqueous vapor to within 1 per cent. {Z. 

 0. G. M., Vol. XV, 1880, p. 1G8.) 



Dines has studied the experimental investigation of the rainfall as 

 observed on various corners of a square tower. Gauges were placed at 

 the 'KE., SW., i^ W., and SE. corners. He concludes that the ratio of total 

 rainfalls on the tower and on the earth dei)ends on the direction and 

 strength of the wind. In calms the differences are scarcely sensible. For 

 a given wind direction the rainfall varies with each position on the tower. 

 The locations which lie on the side next to the wind receive less rain, 

 those on the opposite side receive more rain than if on the surface of the 

 earth. The excess of one side balances the deficit of the other, but 

 whether the mean of both is equal to the true rainfall is not decided. 

 (Z. 0. G. M.J XIV, p. 450.) 



