new standards of weights and measures. 
51 
POSTSCRIPT. 
Since the preceding Paper was read, I have received a 
work on Astronomy, published at Tubingen in 1811, by 
Professor Bohnenberger. This work had been pointed out 
to me by Professor Schumacher as containing a description 
of the convertible pendulum, and a suggestion of its employ- 
ment for the purpose of determining the distance between 
the centres of suspension and oscillation. 
A friend has favoured me with a translation of the part in 
question, by which I find M. Schumacher’s information to 
be perfectly correct, and that the conception of the converti- 
ble pendulum is not so new as I had imagined when I first 
engaged in this enquiry. After demonstrating the recipro- 
city of the centres of suspension and oscillation, the author 
proceeds to say : “ On a cylindrical or prismatic rod C A 
“ (fig. 102.) let there be placed two wedge-formed axes 
“ at C and c, whose edges being turned towards each other, 
“ are perpendicular to the rod and parallel to each other. 
“ Let the one be at the end C of the rod, and the other at c, 
“ distant from C something more than two-thirds the length 
“ of the rod, so that the centre of oscillation 0, about the 
“ edge C, may fall between C and c. On the remaining 
“ part, c A of the rod, let a small weight n, slide backwards 
“ and forwards. Now, by a diminution of the mass of the 
“ rod on one or on the other side, it is easy to manage, that 
“ if this pendulum be suspended on its edge C, a plumb line 
“ hanging down from this, falls upon the edge c, conse- 
“ quently the centre of gravity of the pendulum falls in the 
“ plane of the axis of rotation. By sliding the weight n, the 
