Otto Bolmp. Berlin S. 



13 



The mechanism, which is exposed to view from all sides, is 

 isolated from the external atmosphere by a bell-jar. An india-rubber 

 tube is attached to the side and communicates with the interior of 

 the bell-jar. Barometric changes may be imitated by blowing into 

 the tube or withdrawing air through it, and the movements of the 

 mechanical parts produced by the rise and fall of the barometer may 

 be thus demonstrated and rendered intelligible to an audience. 



Fig. 3 represents in 1 / 4 full size a holosteric barometer (Im- 

 proved Vidi-Barometer), which is specially adapted for metereological 

 observations. The Imperial German Navy has selected and adopted 

 exclusively this instrument from among the so-called metal-barometers. 

 The scale of this instrument is divided in l / 5 mm or Yio Engl. lines, as 

 preferred. By the mechanism the reading is magnified up to 23 times; 

 the fifth part of a millimeter of such a scale reads, therefore, as much 

 as 2 x / 3 mm. Accordingly, very fine measurements may even be made 

 with the naked eye. 



The prices of the above instruments, also those of barometers 

 with altitude scale and metal - thermographs will be found in the 

 price-lists, which may be had gratis and post-free. 



