At that time it was believed, from the best information that could be obtained, that the Cunard steamers carried an average boiler pressure not exceeding 10lbs. to the square inch, and that, to equal them, it would only be necessary to have for the Collins vessels, cylinders of 90 inches diameter and 9 feet stroke with the same boiler pressure, although Mr. Sewell (it is understood) originally advocated 95-inch cylinders. After the contracts were given out to the Novelty and Allaire Works of New York, Mr. Collins procured permission of the government to allow Mr. Faron to visit Great Britain and examine the marine engines and boilers in use there. On his return in the _Niagara_, he discovered that the safety-valves of that steamer were weighted with 13lbs. per square inch, and that with every plunge of the vessel, the valve would open slightly, at once indicating the pressure was equal to the load on the valve. The moment this was communicated to Mr. Collins, he conveyed the intelligence to his engineers, giving a cross section of the _Niagara_ and the dimensions of her cylinder, with 13lbs. of boiler pressure, together with the cross sections of the _Atlantic_, and the _Pacific_ then building. The engineers accordingly recommended that, to _equal_ the Cunard vessel, the dimensions of the cylinder should be 95 inches diameter and 9 feet stroke, the size originally suggested by Mr. Sewell, to which Mr. Collins at once agreed. The engines of the _Arctic_, like those of her sister vessels, were of the “side-lever” kind, with solid cast iron beams, and wrought iron columns and braces. The cylinder, air pump, feed-pumps, shaft-bearing columns, &c., rested upon the bed-plate; the ordinary parallel motion was used to guide the piston-rod, as in the British engines, and the motion was communicated to the cranks by the ordinary arrangement of cross-head, cross-tail, side-rods, and single connecting-rod. The most essential difference from the British method was in the steam and exhaust valves, which were of the “balance poppet” variety, the steam valve being also used for expansion, and working in the several vessels, under the following patents:—on Allen’s cut-off in the _Arctic_ and _Atlantic_; Stevens’s in the _Pacific_; and Sickles’s in the _Baltic_. These engines were greatly admired at the time.