Length of Logarithmic Spiral/Historical Note

Theorem
The length of a logarithmic spiral was first found by in $1645$.

This was the first time anybody had found the length of a non-straight-line curve for anything other than a circle.

Before this had been done, few people could accept that this was possible to do.

For example, had stated in his  in $1637$:
 * Geometry should not include lines that are like strings, in that they are sometimes straight and sometimes curved, since the ratios between straight and curved lines are not known, and I believe cannot be discovered by human minds.

's response was:
 *  Who is so blind as not to see that, if there are two equal straight lines, one of which is then bent into a curve, that curve will be equal to the straight line?