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With reference to our little rods-defined as unit lengths-the

marble slab is no longer a Euclidean continuum, and we are also

no longer in the position of defining Cartesian co-ordinates

directly with their aid, since the above construction can no

longer be carried out. But since there are other things which are

not influenced in a similar manner to the little rods (or perhaps

not at all) by the temperature of the table, it is possible quite

naturally to maintain the point of view that the marble slab is a

"Euclidean continuum." This can be done in a satisfactory manner

by making a more subtle stipulation about the measurement or the

comparison of lengths.