62 GREEN'S STANDARD BAROMETER. 



parts in full, as in the diagrams, not trusting the memory with 

 the whole, until experience shall have given confidence. 



Be careful never to lower the mercury in the cistern much 

 below the necessary quantity, as it increases the risk of air enter- 

 ing the tube. 



When the barometer is to be removed for transportation, or 

 change of position, before taking it down, the mercury is to be 

 screwed up until the cistern and tube are just full. If it is 

 screwed more than this, the mercury may be forced through the 

 joints of the cistern. It should then be inverted, and carried 

 cistern-end upwards. 



This instrument is well adapted for service as a mountain baro- 

 meter, and when used as such, is packed in a leather case, with 

 suitable straps for convenient carriage. 



