APPENDIX. 



123 



Account of the Instruments made ufe of for keeping the 

 Meteorological Journal. 



'nr^HE Marine Barometer was made by Mr, Nairne, 

 -^ from whom I received the following defcription: 



" The bore of the upper part of the glafs tube of this ba- 

 " rometer, is about three-tenths of an inch in diameter, and 

 " four inches long. To this is joined a glafs tube, with a 

 " bore about one-twentieth of an inch in diameter. The 

 " two glafs tubes being joined together, form the tube of 

 " this barometer ; and being filled with mercury, and in- 

 " verted into a ciftern of the fame, the mercury falls down 

 " in the tube till it is counterbalanced by the atmolphere. 



*' In a common barometer, the motion of the mercury up 

 " and down in the tube is fo great at fea, that it is not 

 " pofTible to meafure its perpendicular height; confequently, 

 " cannot {hew any alteration in the weight of the atmo- 

 " fphere : but in this marine barometer, that defeft is reme- 

 " died. The inftrument is fixed in gimmals, and kept in a 

 " perpendicular pofition by a weight faftened to the bottom 

 " of it. 



T 2 «« The 



