Curiosities of Science. 55 



ASTRONOMY AND DATES ON MONUMENTS. 



Astronomy is a useful aid in discovering the Dates of ancient 

 Monuments. Thus, on the ceiling of a portico among the ruins 

 of Tentyris are the twelve signs of the Zodiac, placed according 

 to the apparent motion of the sun. According to this Zodiac, 

 the summer solstice is in Leo ; from which it is easy to com- 

 pute, by the precession of the equinoxes of 50"' 1 annually, that 

 the Zodiac of Tentyris must have been made 4000 years ago. 



Mrs. Somerville relates that she once witnessed the ascer- 

 tainment of the date of a Papyrus by means of astronomy. The 

 manuscript was found in Egypt, in a mummy-case ; and its an- 

 tiquity was determined by the configuration of the heavens at 

 the time of its construction. It proved to be a horoscope of the 

 time of Ptolemy. 



" THE CRYSTAL VAULT OF HEAVEN." 



This poetic designation dates back as far as the early period 

 of Anaximenes ; but the first clearly defined signification of the 

 idea on which the term is based occurs in Empedocles. This 

 philosopher regarded the heaven of the fixed stars as a solid 

 mass, formed from the ether which had been rendered crystal- 

 line by the action of fire. 



In the Middle Ages, the fathers of the Church believed the 

 firmament to consist of from seven to ten glassy strata, incas- 

 ing each other like the different coatings of an onion. This 

 supposition still keeps its ground in some of the monasteries of 

 southern Europe, where Humboldt was greatly surprised to 

 hear a venerable prelate express an opinion in reference to the 

 fall of aerolites at Aigle, that the bodies we called meteoric 

 stones with vitrified crusts were not portions of the fallen stone 

 itself, but simply fragments of the crystal vault shattered by it 

 in its fall. 



Empedocles maintained that the fixed stars were riveted to 

 the crystal heavens ; but that the planets were free and uncon- 

 strained. It is difficult to conceive how, according to Plato in 

 the TimcBus, the fixed stars, riveted as they are to solid spheres, 

 could rotate independently. 



Among the ancient views, it may be mentioned that the 

 equal distance at which the stars remained, while the whole vault 

 of heaven seemed to move from east to west, had led to the 

 idea of a firmament and a solid crystal sphere, in which An- 

 axirnenes (who was probably not much later than Pythagoras) 

 had conjectured that the stars were riveted like nails. 



MUSIC OF THE SPHERES. 



The Pythagoreans, in applying their theory of numbers to 



