302 On Chain Calles or Moorings. 



The following are the proportions of the chain cables on Mf* 

 Bruiiton's principle, 'ompared witli hemp cables. We have 

 copied them from one of the cards circulated by Brunton and 

 Middleton, the mannfacturer.'*, and who warrant tliem : 



■J- inch diameter iron for 9 inch rope proof 12 tons 



1 10 18 



ix 11 26 



11 12 32 



1-rV 13 35 



If II or 15 38 



U U) 44 



li 17 52 



U 18 60 



If 20 70 



2 22 or 24 , . 80 



The above proofs to which the respective sizes are subjected, 

 would break the hempen cables for which each is substituted ; 

 but the chains would bear twice the strain stated, before giving 

 way. They are never, however, exposed, in proof, to a greater 

 strain, and for a good reason — Every strain greater than that 

 to which the vessel for which it is intended could bring upon it, 

 would be an unnecessary exposure to a partial rupturing of some 

 part of the material ; and consecjuently would take from its pri- 

 mitive strength ; which it ought fully to possess when exposed 

 to the regular performance of its dutv. 



On this point we may notice one circumstance so plain that 

 it must strike every man of common sense ; but there are so 

 many fo'il.-, in the world, that too much care cannot be taken to 

 guard against the consequences which might flow from their in- 

 atttntion. A chain made for a certain strain — say as a substi- 

 tute for the cable of a ship pf a given tonnage — should never, on 

 any pretext, be employed for a vessel of greater tonnage. This 

 is a point of so much importance, that it should not in the smallest 

 degree be left to the discretion of any individual to depart from 

 it. The ])ost means, perhaps, that can be devised to prevent an 

 abuse of this kind, and the consec|uences that might flow from it, 

 would be, for the nnderrtriters at Lloyd'sto insist on the exhibition 

 of a pr(iper certificate, to prove that the scale of size has not been 

 departed from, before they admit the ship to be properly equip- 

 ped. If tliis be attsuclpd to, the chain cable will continue ca-v 

 pable of bearing the stiain fur which it ^vas intended, however 

 often repeated, till a failure is induced by fair tear and wear, or 

 ihe actual decay of the material, which would probably require a 

 term longer thaii the snip itself would last. How many hempen 

 cables would be worn oat in that time! If we arc rightly in- 

 formed. West hullaintii, on an average, require their cables ta 



be 



