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Steam Navigation.

Mr. Josias Jessop, of the Adelphi, Civil En­ gineer , called in and examined.

Had no doubt but what the low-pressure boilerwas more secure than the high-pressure, yet,from the natural wear and tear, both were liable toaccidents. If an accident happened to one of ahigh-pressure, its consequences certainly wouldbe more dangerous than that of a low-pressureengine.—Thought that to ensure safety, the boilershould be able to withstand the proof of two orthree times the pressure to which it was after-wards likely to be put, or rather the pressure towhich it should be limited ; if, for instance, it wasmeant to work it at fifty pounds’ pressure, and itstood the proof of one hundred and fifty pounds,the presumption would be that it was secure;but, in the course of two or three years, anyboiler would wear out.—Would recommend anadditional safety-valve, to which the personworking the engine should not have access.—Preferred malleable iron or copper for boilers,because it would not burst by an explosion asbrittle metal would; it w’ould probably rend atthe joints.—Was of opinion that the boiler shouldbe adapted to the shape of the boat; and thatbeing taken for granted, the safety would dependupon the strength of the metal, and not upon theform. It should be made of such strength, thatanv indenture would not affect it. Although theibrm approaching to cylindrical was of course