2X4 THE POPULAR SCIENCE MONTHLY 



ference every year state and city sealers of weights and measures for the 

 purpose of discussing the best methods of securing the use of legal 

 measures of all sorts, and the prevention of frauds by the commercial 

 use of fraudulent weights. The frauds committed against the 

 government by the sugar refiners were nothing in comparison with 

 those perpetrated on the people by short weight in small commercial 

 transactions. 



The bureau has in the field a force of inspectors, cooperating with 

 the state authorities in the detection of fraudulent weights and of short 

 liquid and dry measures. Some of these are used innocently, but many 

 show unmistakable fraudulent intent. The fifth annual conference on 

 weights and measures adopted a resolution favoring legislation requir- 

 ing that all containers be plainly marked to indicate their net content; 

 also that authority be given to the Bureau of Standards by congress to 

 pass on types of weighing and measuring devices used in trade. 



The division of heat has had a particularly arduous task to perform. 

 In contrast to the certainty and permanency of standards of length and 

 mass, and of electrical quantities, there have been great discrepancies in 

 temperature scales and the thermal constants depending on them. The 

 standards used by different makers of thermometers were not in agree- 

 ment with one another, nor did they agree with the accepted gas scale. 

 There were marked differences even between the usual limits of freezing 

 and boiling, or 0° and 100° C. When the work on thermometry was 

 undertaken, a large per cent, of American-made thermometers for tem- 

 peratures as high as 400° to 500° C. were subject to changes of 30° or 

 40° when exposed to the high temperatures they were designed to 

 measure. Further, the average clinical thermometers, used so exten- 

 sively by physicians, were subject to errors exceeding the limit of 

 tolerance. At least 30 to 40 per cent, of the clinical thermometers on 

 the market at the beginning of the work would have failed to pass the 

 requisite test; to-day only about five per cent. fail. The bureau now 

 tests many thousands of them annually. So great has been the improve- 

 ment in American-made thermometers that the German makers are 

 complaining more and more of the loss of American trade in thermom- 

 eters; and some familiar types of mercury-in-glass thermometers are no 

 longer classed as instruments of precision. 



Not only has the bureau authoritatively fixed the scale ranging 

 from 0° to 500° C, but it has met a demand for the accurate measure- 

 ment of very high temperatures by investigating optical and radiation 

 pyrometers, in which the temperature of an incandescent body is meas- 

 ured by the amount of light or heat emitted. The intensity of red 

 light emitted by a body at 1500° C. is over 130 times as great as at 1000° 

 C; and at 2000° C. it is more than 2100 times as great. Hence the 

 possibility of a rough estimate of the temperature of hot bodies in the 



