Christian Era, in the Valley of the Nile. Here, learning was 

 confined to the priests who handed down their knowledge 

 from generation to generation, some of it being preserved in 

 the hieroglyhpies on their monuments. 



The second epoch culminated in the Greek civilization 

 of Pericles, Aristotle, Archimedes and other Greek philosophers, 

 and in the perfection of the arts of Sculpture and Architec- 

 ture. This embraced a period from the fifth to the second 

 century before Christ. 



Arabia and the followers of Mahomet, under the general 

 title of Saracens, developed a high civilization in northern 

 Africa ami southern Europe during the first seven centuries 

 of our era, constituting the third epoch. They founded the 

 world's first University in Southern Spain, and the first Astro- 

 nomical Observatory at Cordova. 



The fourth epoch was the renaissance, beginning with 

 Dante in the thirteenth century, and covering 200 years of 

 wonderful art development in the Italian peninsula. 



The fifth epoch included the work of the greatest mathe- 

 matical geniuses of the world — Copernicus, Kepler, Newton, 

 Laplace, and their contemporaries. 



The sixth epoch embraces the application of science to 

 modern art, and Hie consequent amelioration of the condition 



Of mail. HOLDRIDGL OZRO COLLINS. 



Secretary. 



ASTRONOMICAL SECTION. 



Owing to the absence in Europe of the Secretary, no record 

 was preserved of the proceedings of the Astronomical Section 

 from January to June, 1908. 



The first meeting after the Summer vacation was held on 

 October 1!). 1908, jointly with the Geological Section in the 

 lecture room of the University Club. The subject of the eve- 

 ning, "Luni-Solar Influences in Producing Volcanic Erup- 

 tions," was presented by Mr. William A. Spalding in an elab- 

 orate paper, and was generally discussed by a large audience] 



The section assembled for the November meeting at 621 

 Witmer street, and listened to a thoughtful presentation by 

 Mr. Knight upon "Geotherms. or Sources of Heat Beneath 

 and Within the Earth's Crust/' Careful observations made 

 in different countries seem to establish the fact that in shafts 

 sunk to a depth of one mile or more the temperature increases 

 as depth is reached at the ratio of one degree Fahrenheit for 

 every 60 feet of descent. If this ratio of heat-increase per- 

 sists, the temperature at a depth of 45 miles will be about 6,000 

 or 7.000 degrees, great enough to fuse all known substances, 

 and if the pressure of the superincumbent shell or crust 



42 



