152 ON THE VULCANITE BASE 



canizing properties ? Or, if the small amount of 

 iron rust lias any effect in vulcanizing? Or, 

 whether, after using it repeatedly, the water be- 

 comes so charged with sulphur, or other foreign 

 substance, as to make a change of water impera- 

 tive at given periods ? 



In reply to most of these queries, I acknowledge 

 the courtesy shown me by your worthy President, 

 to whom I am indebted for a chemical analysis 

 of this sediment, which proved it to be wholly 

 oxide of iron ; and we cannot expect anything to 

 be held in a solution which is not detected in its 

 evaporated sediment. 



To prevent the inner surface of the apparatus 

 from rusting, a little borax may be occasionally 

 mixed with the water. 



Another point offers a field for investigation ; 

 viz., the use of loose mercury surrounding the 

 bulb of the thermometer. 



It is now used as a medium to give a correct 

 indication on the scale of the thermometer, of the 

 heat within, thereby dispensing with the neces- 

 sity of having the glass bulb come in direct 

 contact with the steam, and it is generally ac- 

 knowledged, I believe, that the result is quite the 

 same. 



The question now arises — Will it, on being 

 exposed to the atmosphere, and a temperature of 

 heat required, deteriorate, and become after a time 

 less sensitive than at first ? 



