Pebruaey 3, 1905.] 



SCIENCE. 



163 



tion to the scientific and technical labora- 

 tories of the country. 



The work of the bureau may be briefly 

 specified under three separate heads as 

 follows : 



1. To acquire and preserve standards of 

 measure and to certify copies of the same, 

 and to test and investigate measuring in- 

 struments and to determine the properties 

 of materials. 



2. To conduct researches and to investi- 

 gate and develop methods of measurement ; 

 to improve instruments and apparatus for 

 physical measurements and to devise new 

 apparatus, especially for use in testing and 

 in precise measurements. 



3. To distribute infonnation regarding 

 instruments and standards to manufactur- 

 ers, state and city sealers of weights and 

 measures, scientific and technical labora- 

 tories, and to any and every one applying 

 for such information. 



These three functions of the bureau are 

 closely interdependent. To acquire a 

 standard in some cases involves an elab- 

 orate investigation and the independent 

 determination of the value of the stand- 

 ard; and to preserve it may involve subse- 

 quent redeterminations of its value to 

 ascertain whether any change has occurred. 

 A new kind of test often involves the in- 

 vestigation of methods of measurement, or 

 the determination of new standards or the 

 construction of a new instrument. Thus 

 research and testing are intimately con- 

 nected in most of the work of the bureau. 



The distribution of information, the 

 third function of the bureau, is accom- 

 plished through correspondence and the 

 circulars and bulletins issued by the bu- 

 reau, and also by the personal visits of 

 people seeking such information. 



The three fundamental standards of 

 measure are those of length, mass and time. 

 The oldest of these is the unit of time, the 

 second. This ancient T;nit has successfully 



withstood every attempt to replace it by a 

 decimal submultiple of the day. The earth 

 itself is our fundamental timepiece, every 

 revolution upon its axis counting off 86,400 

 sidereal seconds, from which we immedi- 

 ately derive our standard second. No 

 clock is so perfect a timepiece as the earth 

 and all the standard clocks in the world 

 are corrected by it. What the astronomer 

 does in determining the time by astro- 

 nomical observations, is to read off the 

 time of day or night by means of a tele- 

 scope on the starry face of the celestial 

 clock. The telescope corresponds to the 

 hour hand of a 24-hour dial (there is no 

 minute hand), and the stars mark the sub- 

 divisions of the dial. The best made clocks 

 of human invention go fast or slow by at 

 least some fraction of a second each day, 

 but there is no proof to show that the ter- 

 restrial clock deviates by so much in a 

 thousand years. Thus the unit of time is 

 a natural unit, easily obtained direct from 

 nature and universally employed the w'orld 

 over. 



The Bureau of Standards does not in- 

 tend to make independent time observa- 

 tions, but will correct its standard clocks 

 from the observations made at the neigh- 

 boring Naval Observatory. 



The unit of length has a very different 

 history. The foot has been the most wide- 

 ly used measure of length, both in ancient 

 and in modern times. It w^as derived, as 

 the name suggests, from the length of the 

 human foot and is thus a natural unit like 

 the second; but, owing to the multiplicity 

 of human feet and their varying dimen- 

 sions, this unit has varied greatly in differ- 

 ent countries and in different ages, its 

 length ranging all the way from the an- 

 cient Welsh foot of nine inches to the Pied- 

 mont foot of twenty inches. In modern 

 times it has varied from the Spanish foot 

 of less than eleven inches to the Venice foot 

 of over thirteen inches, almost every coun- 



