302 Mr. Tredgold on the Weights and Measures. 



induratissimis acutioribus confertioribus et fere sem- 

 per spiraliter tortis, apice ipso aculeatim-pungenti. 



Genus post prius locandum. 

 yiigra. A. (rough black) foliis multifariis horizontalibus con- 

 10. fertissimis cordato - acutis, verrucoso-rugosts atroviri- 

 dibus. 



Obs. A. foliolosae proxima. Folia involuto-concava 

 undique scaberriraa margine tuberculato. Suffrutex 

 erectus nunc trientalis solum, et induratissimus. In- 

 ter Apicram foliolosam et asperam locanda. 



LI. On the Weights and Measures. By .Mr. Tho 3 Tredgold. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



THHE time will now soon arrive when an important change 

 -*- is to take place in our measures of capacity, and I have 

 been surprised to see so little notice taken of the subject. I 

 have endeavoured as far as possible to recommend by practice, 

 a new system of measuring capacity to engineers, because it 

 appeared to me better adapted for every purpose which they 

 have occasion to consider. It consists in adopting the cubic 

 foot instead of the gallon as a measure in hydraulic and other 

 calculations. A little perseverance soon renders the cubic 

 foot as familiar as the gallon, and it saves time in every kind 

 of calculation, and removes uncertainty. In Smeaton's works 

 you will sometimes find the quantity of water that will serve a 

 water-wheel expressed in wine-gallons, and in other instances 

 his calculations are made in ale-gallons ; and where the kind 

 of gallon is not distinctly stated, it renders it difficult to ascer- 

 tain what measure has been employed. 



In changing the gallon there seems to have been a natural 

 relation of measures of capacity overlooked, which it would 

 have been some advantage to have attended to : I allude to 

 the relation between a cube and its inscribed cylinder. The 

 gallon might have been made one-fourth of the capacity of 

 a cylinder one foot long and one foot in diameter. The cy- 

 linder is the best form for measures of this kind, and it would 

 be very desirable to have a cylindric measure which could be 

 regarded as an unit in all calculations where the areas of cir- 

 cles and contents of spheres are concerned, because our linear 

 measures would apply to ascertain such quantities without re- 

 ducing them into cubical inches. And it seems more natural 

 to found a system of measures on the nature of the things to 



be 



