Steam Navigation. Ill

in case of any sudden collapsation or disengage-ment of steam, also a tube of glass attached to theboiler, which exhibited the level of the water inthe boiler, and precluded any idea of danger inthe minds of the passengers.—Was of opinion thatthe construction of the cast-iron boiler admittedof its being made of wrought iron with equalstrength ; then the explosion of the cast iron onewould be more dangerous, as it would fly inpieces, whereas the other would probably tear.It was scarcely possible to form cast iron every-where equally strong, and if a part be weakerthan the rest, either on purpose or by accident,that would not have the safety that would be ob-tained by a wrought-iron boiler; for instance, incast-iron boilers, it was common to have holes,and if these were filled with some metal of dif-ferent melting temperature from cast iron, morefusible for instance than that, the juncture wouldpart first, and it might be made to tear as awrought-iron boiler would do; and again, thewrought iron was so much more liable to oxyda-tion than cast iron, that although found very effi-cient at first, its strength and tenacity might bevery speedily altered ; for these reasons, cast-ironboilers had been preferred where high-pressureengines were used; and, in small tubes, the tena-city of cast iron could be made greatly to exceedthat which could be given to wrought iron in thesame form.