Feb. 19, 1880] 



NATURE 



377 



ON THE CONSTRUCTION OF A NEW 

 GLYCERINE BAROMETER 



THE direct influence of changes of atmospheric pres- 

 sure on the occurrence of many of our colliery 

 accidents, so clearly demonstrated by the investigations 

 of Messrs. Scott and Galloway, has naturally led to the 

 consideration of barometers affording a wide range of 

 movement, thereby rendering small atmospheric changes 

 a* once apparent, and clearly noticeable to the uneducated 

 eyes of those engaged in such situations as collieries, 

 storm stations, and other places where it is important to 

 note rapid movements without the careful observation 

 which is requisite for the correct reading of an ordinary 

 mercurial barometer. 



Among the various attempts which have been made 

 from time to time to construct long range barometers, may 

 be mentioned the celebrated water barometer, constructed 

 at great cost for the Royal Society in 1830, by Prof. 

 Daniel, but a water column is found to be unreliable in its 

 action, the effects of pressure being so often masked by 

 variations due to changes of temperature on the aqueous 

 vapour existing in the Torricellian vacuum. Mr. Jas. B. 

 Jordan, of the Mining Record Office, has for some years 

 been devoting much attention to this subject, believing 

 that if precise instruments of this class could be made, 

 they would prove of scientific value in showing the 

 character of the more minute vibrations of pressure, and 

 of practical use for the purpose above referred to. The 

 fluid which has shown the most successful results appears 

 to be glycerine — and a glycerine barometer was con- 

 structed by Mr. Jordan in the year 1870, which is still 

 in operation. The purest glycerine, as manufactured 

 by Messrs. Price and Co., has a specific gravity of 1*26 • 

 from its high boiling-point, 440 Fah., it has a very 

 low tension of vapour at the ordinary temperatures of the 

 atmosphere, and a very low temperature is required to 

 freeze it. The mean height of a column of glycerine is 

 27 feet, and a variation of one-tenth of an inch, in the 

 height of a mercurial column is shown by a change of 

 more than an inch in the glycerine column. The glycerine 

 absorbs moisture freely when exposed to the atmosphere 

 but this is prevented by covering the exposed surface or 

 the liquid in the cistern with a layer of heavy petroleum 

 oil prepared especially for the purpose. Barometers of 

 this character have also been constructed by Mr. Jordan 

 at the South Kensington and Jermyn Street Museums 

 with good results. Still further to test the scientific value 

 of the new instrument, application was made to the 

 Government Grant Committe of the Royal Society for a 

 small grant of money to construct an experimental baro- 

 meter, and an instrument was erected therewith at the 

 Kew Observatory, by the permission of the Kew Com- 

 mittee. 



A detailed description of the instrument has recently 

 been read at the Royal Society by the inventor. The 

 accompanying figure explains its construction : the cistern 

 is a cylindrical vessel of copper tinned inside, 5 inches 

 deep and 10 inches diameter, fitted with a screwed cover 

 v,, the air having access through a small hole in the 

 cap, c, attached to the cover, which has a recess, holding 

 cotton wool for filtering out the dust. The main tube is 

 connected with the cistern by attachment (with a soldered 

 joint) to a projecting piece of tube D, which enters the 

 cistern through the bottom, and is fitted at its openin" 

 with a screwed plug, E. The tube is an ordinary corn" 

 position metal gas-pipe, five-eighths of an inch in diameter, 

 furnished at the top with a gun-metal so:ket, into which 

 is cemented a glass tube 4 feet in length, with an inside 

 diameter of 1 inch, terminating in an open cup, and 

 fitted with an in dia rubber stopper. 



The fluctuations of the level of the column of glycerine 

 are observed and read off on brass scales placed on either 

 side of the tube, fitted with indices and verniers, moved 



by milled heads, A A, at the bottom of the scales. The 

 right-hand scale gives inches and tenths of absolute 

 measure from the level of the liquid in the cistern ; the 

 left-hand scale the equivalent value in a column of mer- 

 cury, divided into tenths and hundredths, the hundredth 

 division being equal to about one-tenth of an actual inch. 



The observing part of the barometer is attached to an 

 oak back fixed to the wall of an upper room in the Ob- 

 servatory, the main tube being carried down through the 

 entrance hall to the barograph room below, a distance of 

 27 feet, where the cistern is placed on a bracket on the 



