GREEN'S STANDARD BAROMETER. 



61 



thousandths consequently, are so counted ; the reading s there- 

 fore 29.074. 



Fig. 8. 



. 9. 



29,074 



31 



30 



30,000 



100 



30 



1 



30,131 



Or it may be, as in Fig. 9, where we have 30 inches 1 tenth, 

 and the line on the vernier mark 3 coinciding nearly, but not 

 perfectly, with a line on the scale, it is a little too high ; the 2 

 thousandth short line next above is, however, a like quantity too 

 low ; so the true reading must be the number between them 

 that is, 1 thousandth, making together 30.131. 



These examples include all the combinations the scale allows. 

 A little practice with the barometer, with reference to the ex- 

 amples, will soon enable the learner to read off the scale with 

 facility. At first it will be best to write down the inches and 



