Along with this letter therehas been pre- 

 served among the Cavendish papers the 

 rough draft of the reply to it sent by the 

 philosopher, which is chiefly interesting 

 as an example of the detailed examination 

 which Henry Cavendish continued for 

 some years to bestow upon the sequence 

 and distribution of the geological forma- 

 tions of the southern half of England. 

 With only lithological characters as a 

 guide, he could hardly fail to make 

 mistakes in the order of superposition. 



" I am obliged to you and M r Beatson 

 for the plumbago and to you for your 

 letter. 



I have got some which I received from 

 Wales, part of which, I think, is purer 

 than M r Beatson's. But the rest consists 

 of flakes of a more sparkling nature than 

 Beatson's and less disposed to mark paper. 

 I have also some which I received under 



of the period, was the usual manner in which Michell 

 ended his letters to Cavendish. It is found in the 

 original of his paper of 26th May 1783, which is 

 printed in Phil. Tram. vol. 74 (1784), p. 35. 



59 



