TRANSACTIONS OF SECTION A. 591 



this last being an abbreviated form of 'sixthet of a metre,' just as half-ounce and 

 quarter-inch mean the same as half of an ounce and quarter of an inch. Similarly 

 the measure in which wave-lengths of light are usually measured may be described 

 indifi'erently as 



The tenth metret or as 



The tenthet-metre. 



Either of these is to be preferred to the designation tenth-metre, which the 

 author suggested many years ago,' and which has since been in some degree used. 

 Either tenth-metret or tenthet-metre is correct, but the author himself prefers the 

 latter form. 



In the same way gramets are the decimal subdivisions of the gram. As an 

 example of their use, it is possible by the kinetic theory of gases to arrive at an 

 estimate of the mass of a single chemical atom of each element. That of 

 hydrogen proves to be about the XXV^g— the twenty-fifth gramet, or twenty- 

 fifthet of a gram, i.e., the twenty-fifth of that descending decimal series of which 

 the decigram, the centigram, and milligram are the first three terms. 



For multiples it is convenient to introduce the syllable -o- : thus, in the case 

 of numbers, the name uno-eighteeu will mean 10'^, the number which as ordinarilv 

 written would be 1 with eighteen ciphers after it. (This is about the number of 

 molecules in each cubic miUimetre of air at the bottom of our atmosphere.) The 

 above number may be symbolised by XVIII, and so on in other cases. Again, 

 this_ affix may be appended to such words as metre, gram, &c. Thus the velocity 

 of light in vacuo is to be written 3mVIII/sec., and is to be read ' three metro- 

 eights per second.' In like manner a tonne weight (the metric ton) is the gramo- 

 six, and so on.- 



Other useful affixes are -el and -ane : -el to be applied to British measures of 

 length, -ane to metric. An accordance between British and metric measures 

 of length may be brought about in either of two ways— either by slightlv 

 shortening the British inch, foot, and yard, or else by in an equal degree' lengthen'- 

 ing the metre. In the one case the British foot is shortened do wn^to be e'xactly 

 30 centimetres, in the other case the metre is lengthened out to be exactly 40 inches. 

 The syllable -el may be used to indicate the change required in the yard, foot, and 

 inch. Accordingly the words iuchel, footel, and yardel will mean the inch, foot, 

 and yard shortened in the ratio of 63^ : 62^, or, which is the same thing, in the 

 ratio of 101-6 to 100. On the other hand, the syllable -ane may be ''used to 

 signify an equal change in the opposite direction of metric measures, so that the 

 metrane, decimetrane, centimetrane, and millimetrane are to be understood as the 

 metric measures lengthened in the same ratio, i.e., as 62^ : 63^. With this con- 

 vention as to the meaning of the affixes we may write — 



one inchel = 25 millimetres, 



one footel = 30 centimetres, 



one yardel = 9 decimetres, 

 = (1 -A) metre; 

 and again — 



one inch = 25 millimetranes, 

 one foot = 30 centimetranes 

 One yard = 9 decimetranes, 

 = (1 - tV) metrane.' 



(Light in vacuo advances almost exactly one footel in each ninthet of a second 

 of time.) 



' Phil. Mag. for August 1868, p. 138. 



"^ It would, no doubt, be more in consonance with the genius of the English 

 language to call these the eighteenth uno, the eighth metro, the sixth gramo, and so 

 on; but this consideration seems more than balanced by the great advantao-e 

 possessed by the names as given in the text, of distinguishing in the broadelt 

 possible way between multiples and submultiples. 



' The numbers we should otherwise have to use are: inch = 25-4 mm foot 

 = 30-48 cm., yard = 9-144 dm. 



