198 



PROFESSOR FORBES ON THE TEMPERATURE OF THE EARTH. 



Table III. Thermometric Constants. 



No. 



Range of Wide 



Tube. 



Len^h 

 of 1° in 

 inches. 



Inches 



of Fine 

 Tube 

 above 



ground. 



Inches 



of Wide 



Tube in 



Fine 



Tube. 



Degrees 



in Fine 



Tube. 



Length of 

 Fine Tube 

 in inches. 



Length of 



1° in inches 



of Fine 



Tube. 



Degrees of 



Fine Tube 



sunk below 



ground. 



Degree 

 from which 

 the column 

 exposed to 

 external 

 temperature 

 is reckoned.* 



Observatory. 



41-6— 51-0 

 41-0— 51-0 

 36-0— 54-0 

 30-5— 55-0 



39-5— 52-9 

 38-5— 53-2 

 35-0— 55-9 

 26-5— 600 



40-5— 51-5 

 40-7— 50-7 

 370— 53-6 

 31.5_55-4 



Experimental Garden. 



Craigleith. 



41 



40-5 



35 



28-5 



38 

 38 

 33-5 

 25 



40 

 40 

 35.5 

 31 



* This supposes the Atmospheric Temperature to penetrate 9 inches. The tuhes at the surface 

 would have the following readings : — 



41-2 40-7 35-5 29-4 I 38-9 38-2 34-3 25-7 I 40-1 40-5 362 3M 



May 14. 1834. No. 4. Observatory was lowered3°-12, by withdrawing alcohol. May 15, No. 4. 

 Craigleith lowered by 1°.95. Corrected scales were immediately applied. 

 In the above Table, No. 1 is the longest, No. 4 the shortest. Thermometer. 



VI. Corrections of the Obsej-vations. 



It is very evident that the readings of the thermometers cannot indicate ex- 

 actly the temperature of the point corresponding to the centre of the bulb, be- 

 cause the stem between that point and the surface of the ground never has a uni- 

 form temperature throughout ; and the portion of the column above ground is 

 affected by the temperatm-e of the ah* at the moment. Of these two corrections 

 in our thermometers, the latter is by much the most important, which is fortunate, 

 because it is also determined with the greatest accuracy. 



These corrections, however obvious, have, according to M. Quetelet, been 



