68 Supposed Fixity of t?ie Poles. [No. 11, new seeies. 



Dr. Bradley, Astronomer Royal, instituted experiments on this 

 point, connected with his own discovery of the nutation of the 

 earth's axis. As a practical man, he had the very best possible 

 instrument made, and fastened to a wall. With this first-rate 

 instrument he patiently carried on a series of observation, for 

 twenty years ; and, at the end, found a small difference between 

 the polar place at the beginning, and at the end of his observa- 

 tions. As the difference was small, he placed it to the account of 

 the instrument ; affording another instance that a mathematical 

 mind is not always logical. Had it been otherwise he must have 

 formed an opposite conclusion. Let the difference* be 2" in 20 

 years, then 2 X 30 =s 1' X 60 = 1° and 20 X 30 X 60 = 36,000 

 years. That rate of motion, in 36,000 years, would give a degree, 

 or 60 geographical miles. Take \ or 6,000, and then 10 ! or miles 

 is the motion in 6,000 years : too much to be ascribed merely to 

 error ; and in a nearly perfect instrument. 



This indication is confirmed by geology ; for instance a fossil 

 elephant dug up in Siberia, and petrifactions termed hamites 

 found in Europe. Now these hamites are neither more nor less, 

 than the scaly coating of a kind of millepede found in profusion 

 in gardens at Madras, which eat the germ of kitchen herbs, and 

 leave the said scaly coated exuviae every where around. In the 

 Arctic expedition, which first entered Lancaster's Sound, Captain 

 Sabine noted that the limestone rocks were composed of shells of 

 the Venus kind. This shell is tropical : it abounds on the Ma- 

 dras beach ; is found in the water that surrounds the Island ; and 

 is brought, in barges on the Canal, from Pulicat and other places. 

 The earth certainly has turned by a different motion from its diur- 

 nal arc ; latitudes, zones, and climates have shifted ; and the polar 

 places cannot be fixed. 



The motion being very slow, there are efficient means, incessant- 

 ly acting, to restore the earth's spheroidal form. The ocean al- 



* On enquiring for Vince's Astronomy at the Library of the Madras 

 Literary Society, I learnt that the work had been sold. The greatest 

 nutation is 18" during nine years : it then recedes, and becomes small, 

 I do not recollect the exact figure : it suffices that the same is mea- 

 surable 



