584 SEC. 14. METEOROLOGY. 



contains half the quantity of water that it can contain in the state of 

 saturation. 

 The hygrometer is graduated according to " Regnault's " method. 



2868. Hygrometer, modified by Dr. Geissler, with a delicate 

 thermometer on a stand. 



Will. Haak, Ncuhaus am Rennweg, Thuringren. 



2869. August's Psychrometer, on stand. The thermometer 

 divided into tenths of a degree from 30 to +45 C. 



Will. Haak, Neuhaiis am Rennweg, Thuringen. 



2870. Psychrometer, August system, with stand, in a case. 



Ch. F. Geissler $ Son, Berlin. 



287Oa. Psychrometer, August system, with stand, in a case, 

 for travelling. Ch. F. Geissler $ Son, Berlin. 



2871. Early Hygrometer. 



Museum of King George 111., King's College. 



287 la. Oatbeard Hygrometer. G. J. Symons. 



2871b. Old Travelling Hygrometer. G. J. Symons. 



287 Ic. Modern Saussure's Hygrometer. G. J. Symons. 

 287 Id. Mason's Hygrometer. L. Casella. 



287 le. Pocket Hygrometer, in maroon case. L. Casella. 

 287 If. Bine's Hygrometer. L. Casella. 



VII. SELF-RECORDING INSTRUMENTS. 



2872. Barometrograph, or Self-Recording Aneroid 

 Barometer. M. Pillischer. 



The construction of this instrument differs materially from others of a 

 similar nature, by having the entire mechanism placed in a vertical line, 

 whereby friction is reduced to a minimum. 



The aneroid barometer, 18 inches in diameter, has two vacuum chambers; 

 below it is placed the cylinder, carrying a ruled paper coinciding with the 

 scale of the barometer, and driven by a powerful 8-day clock. The pencil 

 point moves up and down upon a metal rod, prompted by the action of the 

 barometer, and, by a simple mechanical arrangement connected with the clock, 

 imprints the changes which occur from hour to hour on the ruled paper. 

 Thus a black dotted undulated line is produced, showing the rise and fall of 

 the barometer. 



