SANTIAGO OBSERVATIONS. 



Ivii 



Planet Mars. 



The vertical diameters of Venus have been obtained in three modes : first, as were those of 

 Mars, just explained ; second, by direct measurement with the micrometer screw of the equatorial ; 

 and third, by the micrometer screw of the meridian circle whilst passing the field of that instru- 

 ment. The magnifying power of the equatorial generally used was 150, sometimes 235 ; that 

 of the meridian circle more frequently 144, though occasionally no more than 79. No correction 

 has been applied to measurements with the latter instrument for thickness of the micrometer 

 wire. A mean of the separate results from the several methods is 'as follows : 



Planet Venus. 



The corresponding observations made at other observatories, and communicated in accordance 

 with the solicitation contained in the ephemeris referred to, pages xxviii, xxix, have also been 

 printed at length in subsequent pages. 



Believing that a discussion of the solar parallax from observations thus made, by one 

 thoroughly competent yet wholly uncommitted respecting the comparative value of the deduci- 

 ble result, would be appreciated and approved by astronomers, Dr. B. A. GOULD, Jr., was solicited 

 to undertake the task, and, having very considerately consented to do so, all the MS. sheets, as 

 prepared for the printer, were placed in his hands during the month of June, 1855. 



J. M. G. 



WASHINGTON, January 1, 1856. 



1 



