Mr. Lubbock on Cask-Gaging. 333 



variations from heat and moisture, and should therefore be 

 constantly compared with standard metallic scales provided 

 for the purpose and kept in protected situations. 



The extreme limits of the error due to the determination 

 of the variety may of course be ascertained by calculatinf the 

 content upon either extreme hypothesis. I find that the con- 

 tent of the cask for which I = 46'9, b = 31*2, h = 26*1, 



by the formula — Z(2Zr + /r) is 116-37 gallons, 



^l(b 2 + h 2 ) is 109-91 gallons, 



showing 6-46 gallons as the difference between the content 

 obtained, according to one or the other hypothesis. This 

 error may be greatly diminished by ascertaining experimen- 

 tally the correction required for any particular cask, when 

 one or the other hypothesis has been used, which proceedin<>- 

 is facilitated by the circumstance that casks coming from the 

 same country generally maintain a separate and peculiar cha- 

 racter, so that a particular correction might be easily de- 

 duced for a sherry butt, a port pipe, &c, without any re- 

 ference to mathematical considerations. This would amount 

 to the same as to deduct a certain quantity from the length of 

 the cask, calculating the content as though it were accurately 

 of the first variety. So if the brandy piece be, in fact, of the 

 variety which I call the fourth, namely, that of which the con- 

 tent is given by the expression 



it is sufficient to take I = 44-293, that is, to deduct 2*607 from 

 the length, and calculate the content by the expression 



which gives the same result. 



It is in determining the variety of a cask, or the allowance 

 to be deducted from the content previously obtained by con- 

 sidering the cask as of the first variety, that the skill and 

 experience of the gager are principally required. Difference 

 of opinion appears to exist as to the limits of the error which 

 obtains in practice when a single cask is gaged. Mr. Archer, a 

 gentleman particularly qualified by long experience to form 

 an accurate opinion upon this point, has assured me that it 

 generally amounts to 2 per cent., but that by extreme care it 

 may be reduced to a gallon in a single cask, or to 1 per cent, 

 nearly; on the other hand Mr. Nairn, the principal gager of 

 the St. Katherine Docks, in a communication with which be 

 has favoured me, considers the usual error at no more than 

 the eighth of a gallon. 



