July 19, 1912] 



SCIENCE 



77 



possible bearing on field studies during the 

 present season. V. E. Shelfobd, 



W. 0. Allke 



TEE SELATION OF TEE EOESEPOWEB TO 

 TEE KILOWATT' 



There was, before 1911, no precise defini- 

 tion of the horsepower that was generally ac- 

 cepted and authoritative, and different equiv- 

 alents of this unit in watts are given by vari- 

 ous books. The most frequently used equiva- 

 lent in watts, both in the United States and 

 England, has been the round number, 746 

 watts; and in 1911 the American Institute of 

 Electrical Engineers adopted this as the exact 

 value of the horsepower. It is obviously de- 

 sirable that a unit of power should not vary 

 from place to place, and the horsepower thus 

 defined as a fixed number of watts does in- 

 deed represent the same rate of work at all 

 places. Inasmuch as the " pound " weight, as 

 a unit of force, varies in value as g the ac- 

 celeration of gravity varies, the number of 

 foot-pounds per second in a horsepower ac- 

 cordingly varies with the latitude and alti- 

 tude. It is equal to 550 foot-pounds per sec- 

 ond at 50° latitude and sea level, approxi- 

 mately the location of London, where the orig- 

 inal experiments were made by James Watt 

 to determine the magnitude of the horse- 

 power. 



The " continental horsepower," which is 

 used on the continent of Europe, differs from 

 the English and American horsepower by 

 more than 1 per cent., its usual equivalent in 

 watts being 736. This difference is historic- 

 ally due to the confusion existing in weights 

 and measures about a hundred years ago. 

 After the metric system had come into use 

 in Europe, the various values of the horse- 

 power in terms of local feet and pounds were 

 reduced to metric units and were rounded off 

 to 75 kilogram-meters per second, although 

 the original English value was equivalent to 

 76.041 kilogram-meters per second. Since a 

 unit of power should represent the sanqie rate 



^ Abstract of Circular of the Bureau of Stand- 

 ards, No. 34; June, 1912. 



of work at all places, the " continental horse- 

 power " is best defined as 736 watts ; this is 

 equivalent to 75 kilogram-meters per second 

 at latitude 52° 30', or Berlin. The circular 

 gives tables showing the variation with lati- 

 tude and altitude of the number of foot- 

 pounds per second and of kilogram-meters 

 per second in the two different horsepowers. 

 These values, 746 and 736 watts, were 

 adopted as early as 1873 by a committee of the 

 British Association for the Advancement of 

 Science.' The value, 0.746 kilowatt, will be 

 used in future publications of the Bureau of 

 Standards as the exact equivalent of the Eng- 

 lish and American horsepower. It is recog- 

 nized, however, that modern engineering 

 practise is constantly tending away from the 

 horsepower and toward the kilowatt. The 

 Bureau of Standards and the Standards Com- 

 mittee of the American Institute of Electrical 

 Engineers recommend the kilowatt for use 

 generally instead of the horsepower as the 

 unit of power. 



TEE IMPERIAL UNIVEBSITIES CONGBESS 

 The Imperial Universities Congress was 

 opened by Lord Eosebery on July 2, at the 

 University of London, South Kensington. 

 As we learn from the reports in the London 

 Times the question of the division of work and 

 specialization among universities was dealt 

 with in a paper by Sir Alfred Hopkinson, 

 and Sir Arthur Eiicker and Sir Charles 

 Waldstein spoke on the same subject. Prin- 

 cipal Peterson, of McGill University, intro- 

 duced a discussion on inter-university ar- 

 rangements for post-graduate and research 

 students. 



On July 3 there were two sessions of the 

 congress, Lord Curzon of Kedleston presiding 

 in the morning and Mr. Balfour in the after- 

 noon. Papers were read on the relation of the 

 universities to technical and professional edu- 

 cation, the interchange of university teachers, 

 and the problem of universities in the east. 

 The speakers and readers of papers included 

 Sir Frederick Lugard, Sir Isambard Owen, 

 Dr. A. E. Shipley, Sir Thomas Ealeigh and 



