72 



HISTORY OF SCIENCE. 



benighted period. The windmill, of which ancient authors make no 

 mention, must have been contrived within this period. The organ 

 dates from the eighth or the ninth century; and the art of making paper 



FIG. 27. THE CATHEDRAL OF AMIENS (THIRTEENTH CENTURY). 



from rags began to be generally practised, by aid of mechanical appli- 

 ances, about the fourteenth century. But, as already pointed out, 

 the progress made in any art is no evidence of an advance in the 

 knowledge of the scientific principles by which the practice of that art 

 may be explained. That admirable system of architecture which so 

 grandly unites beauty of form to constructive skill arose in this period, 



