II. BAROMETERS. 569 



2800. Meteorological Barometer by Wild, used in all 

 meteorological stations throughout Russia. 



Geneva Association for Constructing Scientific Instru- 

 ments. 



This barometer is a combination of Fortin's barometer, and of Gay-Lussac's 

 old siphon barometer. For minute description, see " Melanges physiques et 

 chhniques, tires du Bulletin de 1'Academie Imperiale des Sciences de St. 

 Petersbourg," vol. ix, 23rd September to 5th October 1875. 



2800a. Barometer of a New System of Construction. 



W. Gloukhoff, St, Petersburg, Ministry of Finance. 



For taking an observation with this barometer, the mercury of the cistern is 

 forced to pass by means of the screw A through the hole a into the open 

 space m n, formed by a glass ring, and to cover its bottom. Then the movable 

 scale of the barometer is lowered so as to bring the steel end C of the scale 

 near the surface of the mercury. Finally, by the screw A the surface of the 

 mercury is made to touch the end C of the scale. The last part of the obser- 

 vation is made in the usual way. 



2800b. Drawing of a Normal Barometer and Mano- 

 meter of the Central Physical Laboratory, St. Petersburg, after 

 the design of Wild, constructed by Brauer, St. Petersburg. 



Dr. H. Wild, Director of Central Physical Observatory, 

 St. Petersburg. 



2800c. Drawing of a Balance Barograph, with tem- 

 perature compensation according to a design by Wild, constructed 

 by Hasler, Berne (Switzerland), registering by electricity every 

 ten minutes. 



Dr. H. Wild, Director of Central Physical Observatory, 

 St. Petersburg. 



2801. Stevenson's Portable Iron Barometer, with Mr. 

 Sang's improvements. Scottish Meteorological Society. 



All the stop-cocks being open, and the plug at lower limb out, fill in 

 mercury till it begins to escape at this opening, shut stop-cock of lower 

 limb, and fill to above upper stop cock of upper limb; shut both stop-cocks 

 of longer limb, put in the plug and open stop-cock at lower limb. The 

 float should then show the true reading as compared with a standard instru- 

 ment. In this way a reading can always be obtained at the most inaccessible 

 stations as accurately as when the instrument left the maker's hand. Designed 

 by T. Stevenson, C.E., F.R.S.E., Honorary Secretary, and described in 

 the Society's Journal, Vol. iv, p. 265. 



28Ola. Capt. George's Improved Patent Mercurial 

 Barometer for travelling. Henry Porter. 



This process of filling by the spiral cord enables the traveller to fill the 

 tube, and produce a perfect vacuum in about 15 minutes, and when the obser- 

 vation is registered the mercury is returned to its iron bottle and. the empty 

 tube returned to its packing of india-rubber and brass tube, so that it can be 

 carried over the roughest country in perfect safety. 



