PLYMOUTH INSTITUTION. 173 



most perfect. In order to show that the hollow centre was a collection 

 of combustible matter in an aeriform state, and consequently inca- 

 pable of supporting combustion, the lecturer introduced the following 

 original experiment : he poured a quantity of spirits of wine on a 

 broad, shallow, copper dish, which when ignited produced a large 

 conical flame; this he bisected near the base, with a piece of watch 

 spring, which became red hot only in the two parts which came in 

 contact with the edges of the flame, shewing that at these parts there 

 was the greatest heat; some camphor was then ignited in a very 

 small metal cup, and was introduced in a burning state into the in- 

 terior of the flame, where it became immediately extinguished, shew- 

 ing that here there did not exist any principle capable of supporting 

 combustion. By means of a small hole in the centre of the copper 

 dish, oxygen was then admitted within the flame, and it was immedi- 

 ately seen that the gaseous matter there contained, combining with 

 a current of gas as it issued from the hole, ignited and burned in a 

 long jet; thus there was one flame burning within the other ; the 

 heat produced by this was very intense; copper and steel wire 

 burned rapidly when brought in contact with it. The lecturer then 

 proceeded to define the nature of fire-damp and the action of wire 

 gauze in preventing the communication of flame from one portion of 

 an explosive mixture through it to another ; the safety lamp was ex- 

 plained, and with it Sir Humphrey Davy's discovery of invisible com- 

 bustion; this interesting phenomenon was exemplified by inserting 

 a red hot coil of fine Platina wire into a glass vessel, containing a 

 few drops of ether in the bottom, the Platina wire was seen to glow 

 very beautifully in the vapour of the ether, once or twice attaining 

 a temperature sufficient to cause it to inflame. The intense heat 

 produced by the combustion of a mixture of oxygen and hydrogen 

 was then shown by means of the oxy-hydrogen blow-pipe : after ex- 

 plaining the construction of this instrument, the lecturer submitted 

 a piece of lime to the action of the flame which immediately ignited 

 it to such an intense degree, as to rival the sun in brilliancy. He 

 concluded by repeating the experiment first performed by himself, 

 namely, that of decomposing the light produced in this way by means 

 of the prism; and exhibited the prismatic spectrum with great brilli- 

 ancy on the ceiling and floor of the hall. 



In consequence of the occurrence of an unfortunate and much to be 

 regretted event, the committee deemed it expedient to postpone the 

 delivery of the remaining lectures until a more suitable opportunity. 



