50 On the Unit of Linear Measurement. By Rev. D. Edwardes. 
perfect and unsatisfactory state of things in this respect than the 
occasion requires. I am probably right in conjecturing that there 
are not many thinking men who are absolutely satisfied with our 
own system, in spite of its many excellent points. Those who have 
to measure minute quantities find the factors of 12 to be of very 
little use, and almost all scientific men are obliged to adopt a 
decimal system between certain limits. It is also difficult to under- 
stand how scientific refinement, if I may be allowed the expression, 
is content to put up with a system of measurement whose unit is 
the length of a “ barleycorn from the middle of the ear.” This is 
theoretically still the case, although in practice a rod equal in length 
to 108 of these primitive barleycorns placed in juxtaposition, has 
been substituted and put by in the Exchequer Chamber for refer- 
ence in case some of Her Majesty’s subjects should find all their 
mid-ear barleycorns not precisely the same length. 
On the other hand, it requires an excess of Fran comania to 
adopt the French metre for our unit. It is true it originated 
with scientific men and not with the agriculturist, but it might 
indeed be contended that the English unit is the more philo- 
sophical of the two. Doubtless there was once upon a time such a 
barleycorn three lengths of which went to make up exactly an inch, 
the thirty-sixth part of the standard yard. But there never was 
and never will be, subject to the present laws of nature, such 
a quadrant of meridian that can be subdivided into 10,000,000 
French metres. The metre again, should it be readjusted, is only in 
a degree better than the barleycorn. For it must vary as the place 
of measurement. The equator is slightly elliptical, and conse- 
quently there can be at most in the same hemisphere but four 
quadrants of meridian which are exactly the same length. Do 
what we may, the metre will only be a local and consequently a 
national unit. It stands to reason that the metre as well as the 
yard must go if we are to have a universal unit. 
The length of a pendulum vibrating seconds is liable to the 
same objection. The experiment must be made at some particular 
spot, and will hold good for that spot alone. Should anything 
occur which would make that spot discoverable only by its longi- 
tude and latitude, complicated elements would have to be introduced 
into the calculations. 
Sir J. Herschel suggested that the diameter of a sphere of the 
same volume as the earth should be taken as unit. The mean dis- 
tance of the earth from the sun might also be suggested for a 
terrestrial as well as a celestial unit ; but the infinite subdivisions 
of these enormously large units would appear at first sight, saying 
the least, somewhat clumsy. Should scientific men meet to discuss 
the matter, there is probably no doubt as to the unit they would 
adopt, namely, the wave-length in vacuum of a particular kind of 
