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on the upper lakes, and deserving of more extensive diffusion where screw-propelling is adopted .- As an example of the extent to which this class of steamers are in use in these inland waters, the fact may be cited, that these works alone have constructed, within the five years last past, over one hundred screw-propellers : the style universally in vogue being constructed by bolting rolled iron blades upon short arms projecting from a stout cast iron centre. The credit of the innovation belongs unhesitatingly to Mr. Horatio O. Perry, the chief engineer of the works, who, in 1850, designed the propeller " Buffalo," with a screw more than half out of water, and she immediately proved herself one of the fastest and most popular on the lakes. It ia. needless to recur to the gratuitous opinions expressed at the time with regard to her probable success. They were the same as always encounter any new enterprise. The "International," which served as a ferry-boat from Black Rock to Brantford, at the upper extremity of the Niagara River, has doubtless attracted the attention of all observing travellers upon that railroad ; her shaft being raised some two feet clear above the surface of the river. More recently, the "Oriental," a vessel of some 950 tons register, has been made the subject of some unsucoessful experiments in other particu- lars, but is now performing with most unqualified success with a screw of the same construction, raised nearly or quite two- thirds out of water, although her draft is such as would allow a deeper immersion if desirable. A little reflection will show more fully the Considerations impelling to this position. The central hub,»the arms, bolt-heads, &c., so far from being eflSicient as propelling surface, are actually and seriously an incumbrance on the vessel's progress when immersed. The portion of screw working in the air at any given time is certainly of no avail in propelling, nor is it, on the contrary, any incumbrance, except by its weight, while of two screws equally immersed, that with the greater diameter will present a considerably larger immersed surface, and the only objectionable features will be its weight and tendency to veer the vessel to one side. The force of the first objection is much diminished by the light construction of the screw ; the iron blades being