246 Observations on Ignis Fatuus. 



evidence of the correctness of the results here given ; the 

 details I am constrained to omit, as they would, obviously, 

 extend this communication to too great a length. 



One gallon, or 231 cubic inches, of this water, when first 

 taken from the well, contains 

 Muriate of soda, - _ . grains 297.3 

 Hydriodate of soda, .... 3. 



Carbonate of soda, .... 19.21 



Carbonate of Hme, .... 92.4 



Carbonate of magnesia, - - - 23,1 



Oxide of iron, 5.39 



grains 440.4 together 

 with a minute quantity of silica and alumina, probably 0.6 

 of a grain, making the solid contents of a gallon amount to 

 441 grains. 



Carbonic acid gas, - - - 316 cubic inches. 



Atmospheric air, .... 4 



Gaseous contents in a gallon, - 320 cubic inches. 



It may be proper to observe, that the gas was extricated 

 from the water, by the application of heat, but was kept in 

 the receiver, at the temperature of 60°, and under a pressure 

 of the atmosphere, indicated by the mercury in the barome- 

 ter standing at 29.5 inches. A part of the atmospheric air 

 was undoubtedly obtained from the tube used to conduct the 

 gas to the receiver. 



Art. V. — Observations on Ignis Fatuus; by Rev. John 

 Mitchell. 



Those luminous appearances, which are popularly called 

 " Will-o'the-wisp" and " Jack-a-lantern," have been alike 

 the object of vulgar superstition and philosophical curiosity; 

 and notwithstanding all attempts to apprehend and subject 

 them to examination, they are not much more the subjects of 

 knowledge now than they were centuries ago. They are 

 still but an ignis fatuus to the philosopher, and a thing of 

 mystery to the credulous. 



I was myself, formerly, familiar with these appearances; 

 they were of frequent occurrence near my father's residence, 

 owing, probably, to the proximity of extensivfe wet grounds, 

 over which they are usually seen. The house stood upon a 



