300 Explosion of an Engine- Boiler, 



portion which passes out at one end is driven forward by t!ie 

 portion passing in at the other. 



In illustration of the change produced in electrical capacity 

 by a change in the constituent parlicU's of a sul)stance, the 

 Doctor remarked how iniperfei;t a conductor metal becomes 

 when oxidated; — that in other substances the conducting powers 

 are increased by an increase of temperature : — thus vapour is a 

 better conductor than water, and water than ice, and the lattej* 

 when at a very low temperature becomes a non-conductor. 



The quantity of electricity existing in the atmosphere. Dr. W. 

 considered to be principally regulated by the proportion of va- 

 pour distributed through the air, dry air i}eing known to be an 

 excellent non conductor ; and to this resistance which electricity 

 experiences with respect to air, the Doctor ascribed the develop- 

 ment of its true principles. Were air a condvK-tor, no electrical 

 changes could occur, since there could not be any accumulation 

 on the one part nor deficiency on the other — we should, in short, 

 be deprived of all the advantages we derive from atmospherical 

 electricity. But as it is, action cannot take place without un- 

 folding a portion of this enlivening principle. The evaporation 

 of a drop of water, equally with the concourse of floating fields 

 of vapour, elicits more or less electricity ; and it is from the 

 process of equalization whicli takes place when showers descend 

 on plants containing different proportions of electricity, that that; 

 action proceeds which excites and stinmlates vegetation. 



Dr.W. conchif't'd by observing that he should apply these prin- 

 ciples to the explanation of the Leyden phial at the next meeting. 



LXXVII. Intelligence and Miscellaneous Articles, 



J'.XPLOSION OF AN ENGINE-BOILER. 



On Friday morning the 4th of April, a most lamentable oc- 

 currence took place at Norwich. Just after the steam packet, 

 bound from that place to Yarmouth, had started, and before she 

 had proceeded twenty yards, the boiler burst with a most dreadful 

 explosion. The boiler was a cylindrical vessel, about eight feet 

 long and four feet two inches in diameter, of wrought iron, ex- 

 cepting one end, which was made of cast iron. The latter gave 

 way, and was propelled towards the stem of the vessel, while the 

 body of the boiler was thrown in a horizontal direction out of the 

 stern, sweeping all before it; at the same time that the concussion 

 of the air and steam completely uin-oofed the vessel from one end 

 to the other. 

 When the explosion took place there were twenty-two people 



on 



