174» Effects of the Precessimi of the Equinoxes. 



mitted to state a few historical facts in support of the theory 

 I advance. 



Tycho Brahe traced a meridian at his observatory, at 

 Uranienburg, which M. Picart found incorrect, and declining 

 to the west. Cassini traced one in the cathedral of Milan, 

 in which the same error is found.* All who have recently 

 determined, by astronomical observation, latitudes and longi- 

 tudes suppose dieir predecessors to have not taken due 

 care, or to have had defective instruments ; and M. de 

 Pouqueville, in his excellent Histm-y of Greece, informs us 

 that the Venetians laid down all the Greek coasts falsely 

 in their charts, in order that the vessels of other nations 

 might be stranded : a hard sentence on the husbands of the 

 Adriatic, which we may probably be able to reverse. 



To put, therefore, my theory to the test, I earnestly entreat 

 that astronomers and persons possessing exact chronometers, 

 will, at the approaching equinoxes, ascertain whether our 

 cathedrals, churches, abbeys, &c., are now in the meridian, 

 and whether old sundials are not also erroneous. If my 

 theory be true, and that they were, when built, erected cor- 

 rectly to the four cardinal points, they will all, without excep- 

 tion, be now found to decline to the west; and from the 

 quantity of the declination the date of their erection may be 

 ascertained to four or five years : this is a new art de verifier 

 les dates, which, if founded in truth, will be of great importance 

 in chronology. 



The communication of the results to your valuable work 

 I earnestly solicit, whether they be for or against me. 



" If right, I'll smile; if wrong, I'll kiss the rod." 

 London, Feb. I. 1832, J. Byerley. 



. * I wrote to our astronomer royal, Mr. Pond, to ask if the meridian 

 which I supposed must have been traced by Flamsteed was now correct. 

 Mr. Pond obligingly informed me that there existed no traces of Flamsteed's 

 meridian at the royal observatory of Greenwich. 



