Half tliP ttem 



Whole of ordinate 



SHIP-BUILDING. 



Area of the Load-Water-Line. 

 Half of ordinate 



Ft. In. 

 - is o 10 

 Y 10 8 



19 6 



26 6 



32 of 



3*5 45 Whole of ordinal 



39 2 



X 



W 



u 



<! T 

 S 

 R 

 O 

 P 

 O 



Half of ordinate 

 Area of the knee 

 X by diftance between the 1 



42 3 



43 8 

 45 6 

 23 3 



ordinate! 



Half of ordinate 



Ft. In. 



O is 23 3 



K 48 3 



F 49 2 



B 49 4 



(0 49 4 



2 49 4 



6 49 4 



10 49 4 



14 49 o 



18 48 9 



22 46 6 



26 22 I 



ordinates 



i 



Area of the load-water-line is 

 Area of the upper horizontal line is 



Mean area .-.--- 



Multiplied by mean depth - . - - - 



Gives folid feet -.---• 

 Which multiplied by pounds in a cubic foot of falt-water 



Gives 



Half of ordinate 



Whole of ordinate 



Half of ordinate 37 



533 ^ 

 X by diftance between the ") ^ ^ ^ 



5870 4 



1 1 15 45 



887 6| 



7873 3i 



7721 ID 



■5)15595 'i 



Number of pounds difplaced below upper horizontal line 

 Divide by pounds in a ton ... 



7797 6| 

 o 6 



3898.776 

 64-375 



250983.725 

 6086151.678 



2240)6337135.403 



Ft. In. 



26 is 22 I. 



27 43 3 



28 42 6 



29 41 10 



30 40 5 

 ^31 39 6 



i 32 38 2| 



33 3<5 3l 



34 34 3 



35 30 oi 

 L3<5 23 4§ 



3 6 



395 3 

 Area of poft and rudder 10 4 



X by didance between 

 the ordinates - 



Area 



405 7 

 I 2 9 



'I '5 42 



Total difplacement of the (hip under the load-water-line - 2829 tons i75lbs. 



We now find that the 74-gun (hip, Plate I., load-water- 

 line, is not only properly placed with regard to her bell fail- 

 ing trim, but the difplacement alfo agrees with the eftimated 

 weight of the whole (hip when fit for fea, which was 28 10 tons 

 745 lbs., or exceeds it by 18 tons 430 lbs., which is better ; 

 as the bias (liould rather lead to increafe than dimini(h in 

 capacity, and favours any little inaccuracies in the admeafure- 

 ments ; though furely there is little room for error in either 

 extreme, if proper attention be paid to the fubjeft. In like 

 manner may, therefore, the weight of any other (hip be 

 found ; and, by reducing the difplacement of the bottom into 

 cubic feet, we may always afcertain if the load-water-line 

 m the draught be properly placed. 



Stability, or Stifnefs. 



The ft.ibility or ftiffnefs of a fhip comes next under con- 

 fideration, being a quality no Icfs efTential to the fafety of navi- 

 gation thai capacity ; and without which a (hip is totally 

 difqualified for the purpofes of war, being unable to ufe her 

 guns with effeft, or carry a prefs of fail in cafe of emergency. 



Before we proceed further, the following particulars, as 

 they relate to vel'els at reft, or in motion, (hould be defined. 



The centre of cavity, or difplacement, already mentioned, 

 is the centre of gravity of the volume of water difplaced 

 by the immerfed part of the (hip's bottom ; and is alfo the 



4 



centre of all the vertical force that the water exerts to fup- 

 port the vedel ; for as heavy bodies by their gravity endea- 

 vour to approach the centre of the earth in a vertical line, 

 patting through their centre of gravity, tending direftly to- 

 wards the centre of the earth ; fo the prefTure of fluids endea- 

 vours to carry bodies in a vei'tical line tending from the centre 

 of the earth towards their furface, and paffing through the 

 centre of gravity of the immerfed part, which forces them 

 towards the furface ; fo alfo in any immerfed body at reft thefe 

 two oppofite forces coincide in the fame vertical line, afting ia 

 a quite contrary direftion to one another. Thus, every float- 

 ing body is necelTarily fupported, or prelTed upwards, by the 

 fluid with a force equal to its weight, or pre(rure downwards, 

 otherwife no body could remain at reft on a fluid, but would 

 afcend or defcend as the prevailing force determined : and the 

 moments of all the forces with which a floating body pre(res 

 on a fluid, and the moments of the forces of the fluid Which 

 fupports the floating body, are equal and contrary, and are 

 refolved into the fame right line, perpendicular to the plane 

 of the fluid. But as this centre depends upon the (hape of 

 the body immerfed, it of courfe varies with every inclination 

 of a (hip ; and whillt the centre of cavity goes falter, and fur- 

 ther over to the (hip's fide in her motions, fo as to keep with- 

 out the perpendicular of the centre of gravity, the (hip will 

 be fupported ; and the water will aft upon the centre of 



cavity 



