given on a late Trial* 323 



very nearly coincided with that of Mr. Wilson, but subse- 

 quent experiments have convinced me that it was oil vapour 

 which we both mistook for oil gas, and that such oil must be 

 heated to a degree which our instruments will not measure, 

 before the oil will be decomposed, or a single bubble of inflam- 

 mable gas liberate(l. 



When Mr. Wilson was examined respecting the repairing 

 of the oil-vessel a few days before the fire, he was asked if he 

 took out the oil for that purpose ; and if, by being so long 

 heated, it had diminished in quantity? To this he answered, 

 " I could observe no decrease but what could be accounted for 

 by the trifling leakage of the vessel." Surely, more decisive 

 evidence of the oil not having been heated improperly could 

 not have been desired ; for if it had been heated sufficiently to 

 have produced decomposition, one part would have been con- 

 verted into charcoal, and another part would have passed off in 

 gas ; the consequence of which must have been, a considerable 

 diminution of the quantity of the oil. 



When asked, what was the appearance of the inside of the 

 retort, or oil- vessel ? he answered, " When we took off the 

 man-hole there was a quantity of carbonaceous matter on the , 

 bottom." " What did that indicate?" " That could only result 

 from the gradual distillation of the oil." Here I apprehend the 

 answer should have been, from the decomposition of the oil, 

 occasioned by the conflagration of the buildings ; because I 

 conceive that charcoal cannot be produced from fixed oil 

 without a portion of the oil undergoing decomposition. 



On Mr. Wilson's evidence respecting the thermometer, it 

 may be remarked, that when the bulb of £^ thermometer breaks, 

 the pressure of the atmosphere, acting upon the column of 

 mercury in the stem, drives it up to the top, provided the 

 vacuum has been perfect, which is always the case in well- 

 made thermometers ; but, as Mr. Scarlett dwelt much upon 

 this circumstance, and endeavoured to turn it to the advantage 

 of the defendants, it may be necessary to observe that the 

 mercury falling out, or remaining suspended in the tube, when 

 the bulb is broken, depends entirely upon the size of its bore ; 



