260 METEOROLOGY AND ALLIED SUBJECTS. 



symbols are constants relating to the thermometers, the specific heat, &c. 

 In its general form, therefore, this formula agrees nearly with that of 

 Apjohn which was based upon an imperfect convection theory. Max- 

 well's theory gives us a clear view of the significance of the numerical 

 co-efficients. In reproducing Maxwell's theory above mentioned, Hanu 

 takes occasion to publish the views of Prof. J. Stefan, as partially 

 given by the latter in 1873, in his "Versuche uber die Verdampfung," 

 and now more fully communicated by him. Stefan's theory is similar 

 to that of Maxwell, but his numerical constants are more carefullv 

 determined especially by means of his own extensive researcbes into 

 the laws of conduction, radiation, evaporation, and diffusion. He finds 



5 or -^- 

 D D 



0.000087 6 for glass, to 0.000097 d for tvater. {Z. 0. G. i)/., XYI, page 



177, 1881.) 



Chistoni has published two memoirs upon the modifications of Eeg- 



nault's formula for wet-bulb thermometer that have been proposed by 



Belli and others. The form at first examined by Belli himself is as 



follows : 



f_f'-{a B-?>)_ (ft B-&) {t-i') ■ 



f—f c-a^ 



but the formulae and constants of Eegnaalt and August equally with 

 this fail to perfectly represent the exact amount of aqueous vapor ; and 

 finally, in his second dissertation, Ghistoni concludes that the following 

 modification of the formulae of Belli 



the ^ or -^ in the above equation to be equal to 1 ; R varies from 



f_ f'-m{t-t'){B-f') 

 l+|(t-t'){B-/') 



gives it quite as accurate as can be desired. {Z. 0. G. 3L, 1881, XVI, 

 p. 82.) 



Jordan has described a new glycerine barometer, which is therefore 

 sensitive in proportion to the diflerence between the densities of glyce- 

 rine and aniline. One such barometer is now in the observatory at Kew, 

 another is established in the museum for practical geology at Jermyn 

 street, a third is in South Kensington, and a fourth is in the ofidce of 

 the London Times. {Z. 0. G. M., Vol. XVI, 1881, p. 26;) 



Sprung has described and elaborated a theory of a self-recording bal- 

 ance barometer, in which a weight supported by a chain replaces the 

 bent-lever arm of Wilds's and otlier forms of this apx)aratus. Ordinarily 

 the barometer tube or its cistern moves up and down in order to register 

 the variations of its pressure, but in the present instrument this move- 

 ment is replaced by that of an auxiliary mechanical arrangement entirely 

 independent of the physical apparatus. As manufactured by Fuess, this 

 barometer of Dr. Sprung is said to give excelleut results. {Z. O. G. JII., 

 Vol. XVI, 1881, p. 1.) 



