258 METEOROLOGY AND ALLIED SUBJECTS. 



tona, describes an improvement upon Edelmann's absorption hygrome- 

 ter and gives tlie formula for computation of the tension of vai^or, as 

 well as observations showing the accuracy' of the apparatus. {Z. 0. 

 0. M., XVI, 1881, p. 319.) 



M. de Lepinay has made a further study of the effect of wind velocity 

 upon the whirling psychrometers (thermometre a froude). He finds that 

 for pressure of 758™"", and temperature from 7° to 20° C,'the formula 



/'—/= 0.525 (f — (/) 



very close!}' represents the vapor tensions observed with the dew-point 

 apparatus. {Z. 0. O. M., XVI, 1881, 217.) 



Hottinger & Co., of Zurich, have adapted a self-register to a Weile- 

 mann or Goldschmid aneroid, and the apparatus has now been tried 

 with great success at a number of European stations. An automatic 

 compensation for its own temperature is introduced and the whole 

 mechanism is of the simplest possible construction ; it goes for ten days 

 without attention. In comparison with other forms of registering bar- 

 ometer, it will be found that the present one is more easily transported 

 and established in its place. The wooden base is replaced with a metal 

 one with adjusting foot-screws; the five vacuum-boxes are, as before, 

 supported vertically one above the other, but they are now held in this 

 position by a strong spring that prevents accidental changes due to the 

 slight shocks received in transportation. The scientific value of the rec- 

 ords of three of Hottinger's barograi)hs has been studied by A. Wolfer, 

 assistant at the observatory in Zurich, who subjected them to large 

 changes in temperature and pressure, and upon comparing their records 

 with simultaneous readings {h^) of the mercurial barometer found the 

 following results, where t is the temperature and x the arc through which 

 the pencil moves and whose versed sine is the quantity measured on the 

 record sheet. 



f [x.) is the computed reduction for the curvature of the arc, and is 

 nearly the same for all instruments, and may be tiiken from a table, 

 such as the following. 



X fix) 



— 20 — 0. 15"°i 







-f20 -0.15 



The formula for barometer Xo. 11 is &« = O.OO-" — 0.995 x + 0.1 (+ — 

 60° F.) 4-/(j:'). The probable error of one reading of the mercurial 

 barometer was i 0.1"^™ ; and that of the corrected barograph reading, 

 was no greater. 



For barometer Xo. 12 the corresponding formula was almost identi- 

 cally the same, and the probable error of a single reading was i 0.15'"'". 



Xo. 13 was studied most minutely and the values of the constants de- 

 termined for all x)ressures and temperatures, thus providing for its being 



