498 



which is altogether new, and contributes to the strength on a totally 

 different principle. When a frame- work has the form of a parallelo- 

 gram, its power to preserve that form depends solely on the strength 

 of the joints ; but when the space surrounded by this outline is filled 

 with the same kind of materials, then every part will sustain a pro- 

 portionate share of any force applied. Accordingly, in the new sy- 

 stem, the openings between the ribs are filled in with slips of timber 

 nearly to the height of the orlop, or lowest tier of beams ; and when 

 these pieces have been fitted, and closely wedged together, they are 

 caulked and pitched over, so as to make the whole frame, from head 

 to stern, to within a few feet of the greatest draught of water, one 

 compact water-tight mass of timber. Hence, even if any of the 

 outer planking of the bottom were to be knocked off, the ship might 

 not only for a time be kept afloat, but permanently be secured from 

 sinking ; whereas, upon the old system, the starting of a plank has 

 been often fatal to the ship and crew. 



In addition to these principal improvements of Mr. Seppings, others 

 of less importance are also described, and some observations are added 

 respecting the economy of the new construction, not only with regard 

 to the quantity of timber necessary, but also the quality, and the fa- 

 cility of replacing any parts that may afterwards be found decayed. 



Remarks on the employment of Oblique Riders, and on other alterations 

 in the construction of Ships. Being the substance of a Report pre- 

 sented to the Board of Admiralty; with additional demonstrations and 

 illustrations. By Thomas Young, M.D. For. Sec. R.S. Read 

 March 24, 1814. [Phil. Trans. 1814, p. 303.] 



Dr. Young observes, that the question respecting the best dispo- 

 sition of the timbers of a ship is by no means so easily discussed as 

 may be supposed by those who have considered the subject but su- 

 perficially ; and deprecates, on the one hand, the forming a hasty 

 determination from a few plausible experiments, as only tending to 

 expose those who are influenced by it to very dangerous errors ; and, 

 on the other, the total rejection of the conclusions formed from such 

 experiments without a minute examination of the objections brought 

 against them. He enters into a detailed enumeration of all the force 

 that can act on the fabric of a ship, and into an exact calculation of 

 the probable magnitude of each in such circumstances as are likely 

 to occur ; and afterwards considers how far the resistances to be op- 

 posed to those forces are sufficient to withstand their action. The 

 strains which occasion the effect of arching are, he observes, of two 

 kinds ; the one derived from the distribution of the weight of the 

 ship, with its contents being not duly proportioned to the pressure 

 of the water ; the other, which has not hitherto been noticed, from 

 the simple and unavoidable application of the longitudinal pressure 

 of the water to the lower parts of the ship only, amounting to more 

 than one third as much as the former, in the case of a seventy-four gun 

 ship of the usual dimensions, being equivalent to the effect of a weight 



