Errors of Types of Minimum Spirit Thermometers. 



435 



6. The absolute minima obtained with cylindrical, hollow- 

 cylindrical, or bifurcated bulbs are probably but slightly affected 

 by ''lag," as the approach to or recovery from the lowest point 

 is generally slow enough to allow them to take up the correct 

 temperature. 



Assuming that the thermometers employed are fair representatives 

 of their respective types, it seems evident that no spirit thermo- 

 meter with a spherical bulb should be allowed in the equipment of 



A 



■03 04 05 



■06 -07 08 09 10 11 



mm 

 P-1 



2 

 3 



















































































5 

 6 



7 































































8 











































Fig. 5. 



a meteorological observatory. Hollow-cylindrical bulbs reduce the 

 errors due to sluggishness by about f. 



In connection with the form and dimensions of the bulb it is 

 interesting to note that the computed values of X appear to bear 

 a simple relation to the radii of the bulbs, irrespective of their form. 

 The radii for the several types of thermometers, taken from 

 Table VII., are- 

 Spherical bulb 8 millimetres. 



Cylindrical,, 3-8 ,, (radius of base). 



Hollow-cylindrical bulb, 1*85 ,, -J (external radius-internal 



radius). 



30 



