92 PLYMOUTH INSTITUTION. 



pipe. Here the most intense heat was produced, though the 

 light of the flame was scarcely appreciable, in consequence of the 

 absence of solid matter. He next explained that the light pro- 

 duced by the combustion of different volatile substances was 

 limited in consequence of the energy of their combination produ- 

 cing only a limited degree of temperature. 



He took the flame of a common candle; — the light produced 

 by this depended upon the temperature to which the carbon con- 

 tained in it was ignited ; this temperature being limited, the 

 ignition was limited. If then this temperature could be increased 

 by extraneous means, the light would be increased in proportion. 

 This was proved by passing the flame of the oxy-hydrogen blow- 

 pipe through the bright part of the flame of th^" candle, the 

 increased brilliancy of which was instantly evident. The 

 same effect was still more strikingly produced by, submitting 

 the flame of spirit of turpentine to the same trial. Light was 

 shown still further to depend on the power of the solid matter to 

 sustain ignition without combustion ; several refractory solid 

 substances were submitted to the action of the oxy-hydrogen 

 blowpipe, and it was found that the light kept pace with the tem- 

 perature up to the point at which they either entered into com- 

 bustion or were volatilized. Lime and magnesia, offering the 

 greatest resistance to the action of the heat, produced consequently 

 the greatest light. 



The lecturer then proceeded to show that when the combustion 

 of the solid matter took place, the liglit diminished; and then 

 explained the conditions necessary for producing the greatest 

 degree of light in the combustion of ordinary flames. 



After detailing to the Society the result of his late investigations 

 on the effects of pressure on flame, which we shall give at length 

 in a future number, the lecturer concluded by enumerating some 

 of the many practical advantages which had accrued to mankind 

 from the researches of philosophers in this department of science. 

 Two of the most prominent were the safety lamp of Sir H. Davy, 

 and the introduction of gas lighting. This latter was illustrated 

 by a small, simple apparatus, in which oil gas was manufactured 

 in a few minutes, in the presence of the society. 



December 18th. — Mr. H. VVoollcombe's Lecture on 

 Public Records. 



Rev. Mr. Rowe's name stood on the card for a Lecture this 

 evening on the Origin and Progress of the English Language — 



