294 SCIENTIFIC Record eor (884 



ters at Haml)urg, Copenhagen, and Munich are about 0.2""". higher than 

 the St. Petersburg standard. {Z. O. G. ill., xviir, p. 359.) 



139. jS^. von Klobulioff describes tbe method of Bogen for filling 

 barometer tubes and explains bis own improvement thereupon. It con- 

 sists, essentially, in attaching to the main tube another glass tube of 

 about equal length by a short flexible-rubber tube. Mercury is poured in 

 througli the latter, and by a proper manipulation the first is filled, with 

 but little chance of leaving auy air bubbles. The method is applicable 

 to barometer tubes of all kinds. Sprung remarks that by warming the 

 mercury the filling is materially assisted. Whipple, of Kew, considers 

 the Bogen method (unless the temperature is elevated somewhat) infe- 

 rior to that of Captain George, who sweeps the bubbles of air out of the 

 tube by means of a feather. The method of Bogen is used to a consid- 

 erable extent at the Hamburg Seewarte. (D. M. Z., i, p. 289.) 



140. Professor Meudeleef, of St. Petersburg, has during the i)ast few 

 years made a large number of improvements in apparatus for measuring 

 the density of the air, as also in barometers, and has done much to deter- 

 mine the law of density of the air at various temperatures and press- 

 ures ; he has among other things shown that as the rarefaction of gases 

 goes on a maximum volume or limit is reached, like the minimum or 

 limit for compression, so that the gas when rarefied does not merg' into 

 the luminous ether, but becomes, so to speak, like a solid body, so that 

 the atmosphere of the earth has a limit. [N'ature, xxvii, p. 5G8.) 



141. n. Dufour and H. Amstein have described a new form of self- regis- 

 tering barometer, based upon a new i)rinciple,and which is distinguished 

 above all others by the simplicity and ease of its construction, as well 

 as by the accuracy and sensitiveness of its records. The principle con- 

 sists in this, that the changes in atmospheric pressure shall alter the 

 position of the center of gravity of a free column of mercurj', and that 

 these changes shall be recorded in the simplest possible manner. The 

 barometer tube is bent at right angles to itself and is fastened to a hor- 

 izontal axis perpendicular to the plane of the bent tube, consequently 

 the lise and fall of mercury in this tube alters its center of gravity and 

 its position of equilibrium. A pointer is attached to the axis, and, turn- 

 ing with it, gives a magnified record of the changes of pressure. The 

 authors call this form of apparatus the "Hebel" or lever barometer. 

 They d(na4op the theory of the barometer and the methods of install- 

 ing and correcting it, and give numerous observations. {Z. 0. G. jI/., 

 XVII, p. 29-i.) 



142. W. Koppen, in some remarks ui)on the use of the barometer as a 

 means of measuring gravity, com]>ares together the suggestions of von 

 Wullerstorf-Urbair, Zoppritz, Siemens, Mascart, and others, and shows 

 how little likelihood there is of deducing from this anything of value in 

 comparison with the pendulum observations of the geodesist. He takes 

 occasion to state that it is much more proper to correct the readings of the 

 mercurial barometer so as to reduce to a standard gravity of 45"^ than 

 to neglect this and apply the reverse correction of the aneroid barom- 



