SHIP-BUILDING. 



The p;eneral rule for calcillating the loading of colliers 

 IS as follows : 



From the length of the keel fubtraft 6 or 7 feet for the 

 dead ftowage fore and aft ; multiply the remainder by the 

 breadth at the midfhip-frame, and that produA by the 

 depth of water the fliip draws when loaded ; divide this 

 by 96, and you will huve the number of London chaldrons 

 the (hip will carry. 



yi method of canjlrut/irig a fcale of folidity, by tvh'ich may 

 he afcevtahud the quantity of -water difplaced at any given 

 draught, and the weight required to bring the Jhip doivn to 

 any draught of -water propofed. 



In order to conllruft this fcale for any (hip, it is requifite, 

 in tlie firlt inllance, to calculate the quantity of water dif- 

 placed by the bottom, behiw each water-line, and by the 

 keel, in the fame manner that we have already done for the 

 74-gini fliip ( Plate I. ) ; for which fliip, as the areas of the 

 leveral water-lines are already calculated, a fcale of folidity 

 may be readily conftrudted as follows : 



Conftrudl a fcale of equal parts, to reprefent tons, as the 

 fcalc fo marked in plate%lV . ; and another to reprefent feet 

 and inches, as that below it. The larger thefe fcales, the 

 more exaft will be tlie performance. 



Draw the line A B, rcprefenting the lower fide of the 

 keel ; and at A fquare up a perpendicular. Then fet up 

 from A B, the deptli of the keel and falfc keel from the 

 flieer-draught, Plate I. ; likewife all the water-lines, D, £, 

 F, G, H, as fhewn in Plate HiW. Jtg. i, parallel from the 

 line A B. 



The following table ia formed by the preceding cal- 

 culations. 



Thus, the firil column is obtained merely by firft inferting 

 the depth of the keel and falfe keel, and adding, fuccef- 

 fively, the dillance each water-line is apart. 



The fecond column is obtained by firll taking, from the 

 foregoing calculations, the cubical contents of the keel and 

 falfe keel, which is 53 1.5 feet, as {hewn in the table at C. 



Then find the cubical contents between the upper fide of 

 the keel and lower water-line, by finding the mean area, and 

 multiplying it by the dillance of the water-line above the 

 keel, which is 3.6 feet, and we have 7254.881, the dif- 

 placemcnt between the lower water-line and the keel : add 

 this number to the former, and the whole will be 7786.381, 

 the difplacement at the lower water-line, or D. 



Again, find the mean area of the firft and fecond water- 

 lines 4442.2655, and multiply it by the dillance between 

 the water-lines (3.6 feet), and add the produft to the 

 former. The fum will be 23778^.537, the difplacement at 

 the fecond water-line, or E. 



In like manner, find the mean area of the fecond and third 

 water-lines, and multiply it by the diftance between. Add 

 the produft to the former, and it will produce 44124.387, 

 the difplacement at the third water-line, or F. Thus pro- 

 ceed with the relt. 



The third column is to be filled up by multiplying each 

 line of the fecond column by the weight of a cubical foot 

 of fea-watcr (645 lbs.), and dividing the produft by 2240, 

 the number of pounds in a ton ; which will, of courle, give 

 the weight in tons and pounds, as in the table. 



Now fet off the tonjiages from the above table upon the 

 correfponding water-lines, &c. in Plate X.IV. Jig. 1, thus: 

 upon C, rcpreicnting the upper fide of the keel, fet oft, 

 from the perpendicular A H, 15 tons 615 lbs., taken from 

 the fcale of tons, equal to C c. Upon the line D, or lower 

 water-line, fet off 223 tons, 1728 lbs. equal to D d. Upon 

 the line E, or fecond water-line, fet off 683 tons 823 lbs. 

 equal to E e. In like manner, fet off the other tonnages 

 upon their correfponding water-lines : then thro\igh the 

 points Cr, D^, Ef, F/, G^, H h, draw the curve A S, 

 which will reprefejit the folidity of difplacement at any 

 given height. 



I 



For example, the 74 {Plate I.) draught of water, when 

 launched, was 1 3 feet forward and 1 7 feet abaft ; which 

 gives 14 feet 3 inches at dead-flat, or midfhips, the (hip's 

 chief fupport in this light (late. Take, therefore, 14 feet 

 3 inches from the fcale of feet, and fet it up parallel from 

 the line A B, or lower fide of the keel, to intcrfeft the 

 curve of difplacement, as at I /. Take the nearell dillance 

 from the interfeftion of the curve to the perpendicular A H, 

 and apply it on the fcale of tons, and it gives 1550 tong 

 1 120 lbs. But by the cllimatc, the weight of the Ihip, at 

 her huinching draught of water, was 1377 tons 2198 lbs., 

 which exceeds the above by 172 tons 1162 lbs. ; but that 



may 



