and on the Nature of the Diamond. 3 1 9 



Calculation by carbonic acid 12-41 

 by oxygen 12'38 



difference -OS 



Here, contrary to what happened in other experiments, the 

 calculation by carbonic acid rather exceeds that by oxygen ; 

 12-58 : 3-50: : 100 : 28-27. 



Calculating therefore by oxygen, 100 grains of carbonic 

 acid contain 28-27 of coal. 



Experiment with Plmnlago, 



Thermometer 44° Fahrenheit, barometer 29-94. 



4 grains of plumbago, from a very fine specimen belong- 

 ing to Dr. Babington, were put into the tray. Our oxygen 

 left a residuum of 2 parts in 100, and we began with 49-&4 

 cubic inches. The tray, with its contents, being placed in 

 the platina tube, was heated to redness for a quarter of an 

 hour, and the gas made to pass over it several times. When 

 all was cool, the original quantity was neither increased nor 

 diminished, and <m withdrawing the tray we found only '2 

 of a grain of oxide of iron ; so that this specimen of plum- 

 bago contains only 3 per cent, oxide of iron. 

 The gas being now examined. 



Lime water absorbed 53 parts from 100 



The tests for oxvgen 42 



Residuum - 3 or an increase of 1 percent. 



100 



Correction for temperature. 

 60° 0-103 49-84 



44 16 l-Gi 



10 difF. 1-648 add for temp. 51-48 



Correction for pressure. 

 30 : 29-94 : : 31-48: 51-37. 

 The quantity of oxygen at the mean would be 51-37 cubic 

 inches. 



100 



