METEOROLOGY AND ALLIED SUBJECTS. 



245 



barometers in Baden. The following* table gives the difterence (Carls- 

 nihe minus portable) as the result of comj^arisous with the portable 

 barometer : 



Date. 



Marcli, 1874. 

 April, 1874.. 

 AuKust, 1874 

 April, 1875.. 

 May, 1875... 

 August, 1875 



Difference. 



mm. 

 +0.54 

 +0.50 

 +0.40 

 +0.00 

 —0.04 

 —0.10 



Date. 



March, 1876. 

 May, 1876 . . 

 August, 1870 

 March, 1877 . 

 Mav, 1877 . . . 

 July, 1877 . . . 



Difference. 



m,m. 



—0.00 

 —0.13 



—0. :;o 



—0.20 

 —0. 10 

 —0.20 



It follows from the above figures that the difference between the two 

 barometers had in the course of three years changed by 0.74'"™, and 

 several considerations go to show that this change has been of the na- 

 ture of a gradual sinking of the mercury within the new tube of the 

 Carlsruhe. During the years 1870 to 1876, a number of inspecting 

 tours had afforded an opportunity of comparing the Carlsruhe barome- 

 ter with the barometers at the other stations. These comparisons show 

 that the Carlsruhe barometer changed but little in respect to the others 

 until 1874, after which date there was a general change in the same 

 direction in their relative standings, the amount of which agrees closely 

 with that previously determined. Sohncke very properly concludes that 

 minute quantities of air and vapor must have escaped upwards into the 

 vacuum chamber of the Carlsruhe barometer, and as this instrument 

 is apparently not in any way inferior to the standards generally used 

 in Europe, it was reasonable to conclude that similar defects occur in 

 other barometers. {Z. O. G. M., 1879, Vol. XIV, p. 141.) 



Schreiber has elaborated the ideas contained in the so-called balance 

 barometer, and has constructed a self-registering apparatus for both 

 pressure and temperature, which, after many months' testing, has been 

 purchased for the use of the German Seewarte, at Hamburg. The in- 

 strument consists of three parts: 1. The barometer on whose theory and 

 corrections the elaborate investigations by Schreiber, in 187G, are already 

 well known. 2. The thermometer for the temperature of the instru- 

 ment, which is constructed like the barometer. 3. The thermometer for 

 the temperature of the air, which consists of a copper vessel, holding 

 5 liters, which is placed outside the apparatus, and is connected with 

 the self-registering portion by means of a small lead tube, which latter 

 enters into a balance manometer within the case with the barometer. 

 The movements of the manometer are recorded in a manner precisely 

 simultaneous with the other two instruments. {Z. 0. G. If., Vol. XIV, 

 1870, p. 480.) 



Schreiber has also devised methods by which the balance manometer 

 can be applied to the registration of a variety of phenomena; and even 

 to the integTation of the registered curves. [Z. 0. G. M., Vol. XIV, 

 1879, p. 487.) 



