NIPHER PROPERTY OF THE ISENTROPIC CURVE. 407 



down to this day, and I myself have seen the nativity of a converted 

 Tamulian, written some years ago. The Chinese astrologers are 

 known, but it is a new and remarkable accession that Kingsbor- 

 ough's Mexican and the American antiquities discovered near 

 Davenport, Iowa, represent similar planetary configurations, as 

 will be demonstrated in another place. 



These certainties that in all quarters of our globe planetary 

 constellations have been observed and expressed quite in the same 

 way, and that many of them incontrovertibly concern the year 

 2780 and even 3446 B.C., constrain us to believe that ancient 

 astronomy must have proceeded from a primitive nation in Asia, 

 as Cicero and the Georgian Chronicle in Journ. Asiat., Paris, 1833, 

 p. 535, state. The Greek astronomical papyrus commented on 

 in the author's Astronomy, p. 212, assigns this science to the 

 primitive savans of Chaldaea, and this is ascertained by the fact 

 that our actual constellations exactly agree with those of the an- 

 cient Chaldeans and Egyptians, 



On a Properly of the Isentrofic Curve for a Perfect Gas 

 as drawn upon the Thermodynamic Surface of Pressure, 

 Volume, and Temperature * 



B3' Francis E. Nipher. 

 The equation of this thermodynamic surface is 



pv = RT, .... (i) 



where p^ v, Z'repi-esent the pressure, volume, and absolute tem- 

 perature, and where R is directly proportional to the volume of 

 a unit mass (or inversely proportional to the density) of the gas 

 at a standard temperature and pressure. 

 By differentiation (i) becomes 



dp = ^ dT - ^^dv . . . . (2) 



V v^ 



For convenience putting 



V v^ 



* Read April 3, 18S2. 



