MEDIEVAL COSMICAL PHILOSOPHY. 163 



London was his own disciple, "nurtured and instructed 

 for the love of God," and the trusted bearer of his com- 

 pleted works to Rome in 1267. For John, Bacon predicted 

 a glorious future "if he live to grow old and goes on as he 

 has begun." But upon Peter this Picard from Maricourt 

 he lavishes all his praise, all his enthusiasm. And 

 Master Peter had well deserved it. From the trenches be- 

 fore Lucera he had written an epistle, which later came to 

 be known as the "Letter of Peter Peregrinus" a missive, 

 little remembered now, often misunderstood, often plagiar- 

 ized centuries ago, more often misinterpreted, but none the 

 less a great epoch-making deliverance an imperishable 

 landmark in the path of physical discovery. 



Before entering upon the examination of this work, a 

 brief reference to some features of the generally accepted 

 cosmical philosophy of the Middle Ages is here necessary. 

 That our globe was the centre of the universe, and thus 

 fixed and immovable, was undisputed. Encompassing it 

 were supposed to exist ten heavens, successively envelop- 

 ing one another ; all except the outermost being in con- 

 stant rotation about their common centre. The highest 

 or external heaven formed the boundary between creation 

 and space, and here abode the Deity, forever hearing the 

 harmony of the spheres which lay below Him, in an endless 

 hymn of glory and praise. Beneath the Empyrean came 

 the crystal heaven, or primum mobile, then the heaven of 

 subtle elements without weight, constituting the fixed 

 stars, while the successive inner shells were respectively 

 the heavens of Saturn, Jupiter, Mars, the Sun, Venus, 

 Mercury, and, finally, of the Moon ; the Earth and its 

 atmosphere being sublunary things. All motion of these 

 heavens was the direct work of angels or intelligences, 

 and the laws of Nature were merely divine precepts which 

 they carried into execution. 



Ages, however, before these notions were conceived, the 



