Following up Professor John Henry's comment, I find the following  
literature regarding the early history of the English patent system  
quite useful. 
 
Christine MacLeod, Inventing the Industrial Revolution: the English  
patent system, 1660-1800, Cambridge; New York: Cambridge University  
Press, 1988.  
 
Hope this helps. 
 
Masazumi Wakatabe 
Waseda University