SOLID MEASUREMENTS. 233 



round forms, which is scarcely so great as with the linear-measure. 

 They also depend on having square ends that is, on the bottom or 

 top being set perfectly square to the edges. Still a very considerable 

 degree of accuracy is to be obtained by these methods. 



With the purely geometrical modes of measurement by means of orcli- 

 nates I need not detain you, but I should be neglecting a very large part 

 of the subject, if I were to fail to call your attention to some very 

 important economical measures, namely, timber measuring and cask 

 gauging. In timber measuring, practically, one's first idea of measuring 

 a spar is to consider it as a cylinder. Of course any spar, as the tree 

 grows, is considerably thinner at one end than at the other, but the 

 correction for that is not very difficult to apply, and is ordinarily 

 applied by geometry, with which I need not trouble you here, parti- 

 cularly as we have before us no instruments for doing it. Sliding rules 

 are used for the purpose, but they are rather calculating than measuring 

 instruments. With regard to cask gauging, however, it may be done 

 with as much accuracy as the subject admits of. It has been made 

 the subject of very elaborate calculation by Hutton and others, and 

 great perfection has been obtained in the instruments with which the 

 measurements are taken, considering the mode of applying them. 

 The instruments I am now showing are those manufactured by Messrs. 

 Bring & Fage for the use of the English Customs and Excise officers. 

 This is the calliper with which the length of the cask is measured. Of 

 course the staves generally stick out an inch or two beyond the head 

 of the cask, and consequently the length is measured by two rules 

 sliding one upon another, which fit over the head of the cask, and enable 

 you to get a fairly accurate measurement of the length. The calliper for 

 obtaining the diameter of the cask is also here. It is constructed on 

 the same principle as the first. In getting the diameter of the cask 

 we have first to get the bung diameter, the diameter at the widest point, 

 and also at the head, and these are quite different. I only mention 

 for the sake of those who are not acquainted with round measure, 

 that it is necessary that the callipers should be applied in several 

 places : you have either to turn the cask or turn the calliper round the 

 cask, because you very seldom find that the cask is a perfect circle, 

 and for the measurement you have to take the average. Then when 

 you have got the diameter of the cask at the bung and at the head, 



