Excerpt from Journal of the Franklin Institute of the State of Pennsylvania, Vol. 12: And American Repertory of Mechanical and Physical Science, Civil Engineering, the Arts and Manufactures, and of American and Other Patented Invention

The facts and considerations, which have been adduced in the foregoing examinations, are probably sufficient to sustain this position, but I prefer, for further illustration, to compare the construction of these light steamers with that of the magnificent steam ships of class A. Now the floor frames or timbers of classes C and D, forming the base of construction, are moulded nearly, if not quite, as deep as those of the steam ships, but are sided, however, to a much reduced width or thickness, thus affording a more advantageous selection and application of the material, and dispensing with an unnecessary and injurious weight. Instead of half floors and double-futtocks, by which the frames of the ships are often greatly weakened, nearly all the timbers of class C are whole at the keel, and extend to the sides of the vessel, where, by means of a well selected and proportioned futtock, and top timber, the frame is extended to the deck with but one joint or breakage, which is most strongly supported. It is probable, however, that the frames of either of the four classes in the table have strength much more than sufficient to resist any external pressure or other strain which can possibly accrue to a water borne vessel, properly loaded. But the actual strain upon the frames of each class in a sea-way, the length being equal, will be nearly in proportion to the square of the diameter of the vessel, and its entire weight, except as this strain may be increased by the want of heavy plunges and active buoyancy. Hence, although there is more space between the frames of the light classes than in the heavy steam ships, yet the available strength of the frames and other material, as compared with the weight and amount of strain respectively, will be found greater than in the class of heavy built steam ships.

In regard to the longitudinal frame work and the keelsons, by which the lateral frames or ribs are connected together in one firm structure, I may state that the keelsons of the light classes are as numerous as in the large steam ships of three times their tonnage, and four times their weight, and that the sizes of these keelsons are, at least, in equal proportion to the weight of the vessels: while the longitudinal framing at the turn of the bottom or bilge, and also at the line of the deck, parts of vital importance to the strength and security of a steam vessel, exceed, in comparative strength, security of fitting and longitudinal tenacity, those of any other vessels known. These connexions are bound together, laterally, in the strongest manner, by large screw bolts passing through the frames from outside to inside, no less than four thousand of these bolts being sometimes used in the construction of a common steamer. The framing and securities of the decks of these steamers are also arranged in such a manner as to dispense with a great amount of unnecessary and injurious weight, while their durability and available strength are thus greatly increased.

Thus it will appear that these steam vessels are constructed and secured in a manner well calculated to relieve the frames and planking from injurious strain in a sea-way.

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