370 
Proceedings of the Royal Society 
objections to results deduced from the Great Pyramid, — but the 
objections are founded on such erroneous principles of practical 
science, that I notice them only for the sake of the Royal Society 
of Edinburgh, in whose publication they now appear. 
The first objection is, that the theoretical and actual sizes of 
the supposed standards of the Pyramid “ are made to vary in 
u different books, which it is impossible for an actual standard to 
do.” (p. 265.) 
Yet it is a notorious fact that the theoretical and recorded sizes of 
the actual national standards do vary in different books and even 
sometimes in the same book ; and this, whether T^e take the pages 
of micrometric measures for the length of our standard yard from 
the Philosophical Transactions, or the Memoirs of the Royal Astro- 
nomical Society, and compare these with the different ideas of the 
savants of various countries, at different times within the last 100 
years, as to the true length of a pendulum vibrating seconds in a 
particular position on the earth, (the British yard’s theoretical 
reference) ; or whether we enter into the conflicting ideas of the 
French nation, at successive epochs, as to the real length of a 
ten-millionth of the earth’s meridian quadrant, and its proportion 
to their standard metre, at different temperatures. 
Thanks to the exertions of the many great men who have 
laboured splendidly in the cause both of the theory and practice of 
such standards, — the differences of the modern standards alluded 
to, are now reduced within very narrow limits. But differences 
to some extent there are still, and will be for ever, according to the 
nature of things, touching all practical standards, their theoretical 
references, and every subsequent, additional determination of the 
numerical value of the same,— if pushed to sufficient refinement, 
and whether by one or many observations. 
The more man strives after practical perfection, the more im- 
possible it is found to attain to it. An uneducated countryman 
thinks he has the time perfectly , if he knows it to the nearest 
minute. But an astronomer, though he obtains the time by ob- 
servations to a fraction of a second, yet always finds his results 
attended by some still smaller fractional portion of error. Again, 
a carpenter compares two specimens of three-foot rules, and if they 
agree within half of T ^th of an inch, he at once pronounces them 
