590 REPORT— 1894. 



in practical work to the O.G.S. system. In the M.M.S. system the fundamental units 

 are — 



A massein of ten kilograms (the myriagram) ; 



A lengthein of one metre ; and 



A timein of one second ; 



whence we obtain, as derived units — 



The velocitein = one metre per second ; 



The densitein = ten grams per litre, in which unit the maximum density of 



water is 100 ; 

 The forcein = one hyper-kilogram ; and 

 The energein = one hyper-kilogrammetre. 



Inasmuch as the engineer, if he uses metric weights, determines all his forces in 

 kilograms and measures energy in kilogrammetres, the M.M.S. system is the most 

 convenient for him. He has only to increase each of these measures hj TO per 

 cent, to have his determinations expressed in hyper-kilograms and hyper-kilo- 

 grammetres, i.e., in systematic measures adapted to any dynamical calculation lie 

 may have occasion to make. It is also deserving of note that this system is more 

 conveniently related than the K.M.S. system to the C.G.S. system, "in which our 

 best tables have been computed. This arises from the circumstance that \/LM 

 a physical quantity which is constantly turning up in the dimensional equations of 

 electricity and magnetism, is in the M.M.S. system an exact decimal multiple o'" 

 what it is in the C.G.S. system. The relation here pointed out is of impoitance 

 to the electrician. 



The use of the prefix hyper- has the additional advantage of keeping steadilv 

 before the mind of the student the actual amounts of the measures of force and 

 energy with which he is dealing, and thus helps him to make his conceptions cor- 

 respond to the facts of nature. The amount of each measure is not brought into 

 view by such names as dyne and erg unless supplemented by such names as byper- 

 milligram and hyper-fifthet-grammetre, and is apt to be lost sight of in using the 

 C.G.S. system. 



The author was a member of the Committee of the British Association, which in 

 1873 recommended C.G.S. measures for general adoption by physicists. He put 

 forward in competition with it the K.M.S. system, spoken of above, and also 

 advocated the use of the prefix hyper- to be employed as described in this paper. 

 It is correctly recorded in Everett's ' Units and Physical Constants ' that he dis- 

 sented from the choice made by (he Committee, but "the reason for his dissent is 

 not correctly indicatfd. His main objection was that this choice needlessly led to 

 such out of the luay values for the dyne and erg — needlessly, because other choices 

 might have been made, such as of either the K.M.S. or the M.M.S. system, 

 which, while equally adapted to the sciences of electricity and magnetism, would 

 have been free from this great inconvenience in dynamics. He regrets to have 

 observed tliat the choice that was then made has retarded the use of systematic 

 measures by practical men and even by students, and hopes that this may in some 

 degree be remedied by the suggestions made in the present paper. 



Another useful suffix is -et, meaning decimal submultiple. As applied to 

 numerals it gives us such suitable names as sixthet, tenthet, seventeenthet for a 

 unit in the sixth, tenth, and seventeenth places of decimals, which are otherwise 

 expressed as lO"", 10-'°, lO-^'. A convenient symbolical representation is VI<^ , 

 X^, XVII^, the symbol ^ being very easily written and being what in Sir Isaac 

 Pitman's system of shorthand spells thet, so that YI^, X<, XVII^ are to be read 

 sixthet, tenthet, seventeenthet. 



The suthx -et may also h<^ appended to the names of measures, e.g., metrets are 

 the decimal subdivisions of i he metre. These in their order are to be spoken of as 

 the decimetre ; th^ centimetre ; tbe millimetre; the IV^m, the fourthet-metre, or 

 fourth metret; the V^ m tifthet-raetre, or fifth metret; and so on. Thus the 

 micron used by microbe pists may be described either aa 



The sixth metret or aa 

 The sixthet-metre, 



