UNITS. XXXVll 



" In view of these facts, and the absence of any material normal standards of 

 customary weights and measures, the Office of Weights and Measures, with the 

 approval of the Secretary of the Treasury, will in the future regard the Interna- 

 tional Prototype Metre and Kilogramme as fundamental standards, and the cus- 

 tomary units, the yard and the pound, will be derived therefrom in accordance 

 with the Act of July 28, 1866. Indeed, this course has been practically forced 

 upon this office for several years, but it is considered desirable to make this for- 

 mal announcement for the information of all interested in the science of metrology 

 or in measurements of precision. 



T. C. Mendenhall, 

 Superi7ttendent of Standard Weights and Measures, 

 " Approved : 



J. G. Carlisle, 



Secretary of the Treasury. 

 April 5, 1893." 



No ratios of the yard to the metre and of the pound to the kilogramme have as 

 yet been adopted by international agreement; but precise values of these ratios 

 will doubtless be determined and adopted within a few years by the International 

 Bureau of Weights and Measures. In the mean time, it will suffice for most pur- 

 poses to use the values of the ratios adopted provisionally by the Office of Stand- 

 ard Weights and Measures of the United States. These values are — 



I yard = %%%^ metres, or i metre = §§j|5 yards, 

 I pound = M§^§ kilogrammes, or i kilogramme = faSoo^ pounds. 



These ratios were legalized by Act of Congress in 1866. Expressed decimally 

 these values are * — 



I yard ^ 0.914402 metres, i metre = 1.093 6x1 yards, 

 I pound = 0.45 359 kilogrammes, i kilogramme = 2.20462 pounds. 



The above values of the relations of the standards of the British and Metric 

 systems of units are adopted in this work. Tables i and 2 give the equivalents 

 of multiples of the standard units and also equivalents of multiples of the derived 

 units of surface and volume. These tables are published by the Office of Stand- 

 ard Weights and Measures of the United States, and are here republished by per- 

 mission of the Superintendent of that Office. 



2. British Measures and Weights. 



a. Linear measures. 



The unit of linear measure is the yard. Its principal sub-multiples and multi- 

 ples are the inch ; the foot ; the rod, perch, or pole ; the furlong ; and the mile. 

 The following table exhibits the relations among these measures : — 



* The actual error of the relation of the yard to the metre may be as great as 1/200 000th part, 

 and the actual error of the relation of the pound to the kilogramme as great as i/ioo 000th part. 



