COMPARISON OF LATITUDE OBSERVATIONS AT 



SAYRE OBSERVATORY, SOUTH BETHLEHEM, AND AT 



FLOWER OBSERVATORY, PHILADELPHIA, 



From September 30, 1904, to September 3, 1906. 



By JOHN H. OGBURN. 



(Read April 20, 1907.) 



This paper is based on two years work on latitude determination 

 at Bethlehem compared with that obtained during the same period 

 at Flower Observatory, the results of which Professor Doolittle has 

 kindly furnished me in advance of publication. 



The Sayre Observatory at South Bethlehem, under Professor 

 Doolittle's direction, was among the first to be devoted to this class 

 of work and the observations, continuing through a period of nearly 

 twenty years, resulted in a series which has been an invaluable aid 

 in the discussions of the laws of the variation of latitude. It was 

 thought that a continuation of the same class of work for some 

 years might be desirable as it would result in a longer series at a 

 given point than could be found elsewhere. 



To aid in this project, the late Mr. Robert H. Sayre, one of the 

 trustees of Lehigh University, furnished the means for procuring 

 a modern zenith telescope and a suitable house for it. 



The zenith telescope house was erected in the spring of 1904 

 according to plans which conform to those of the International 

 Latitude Stations and is composed of wood excepting the roof which 

 is of tin. The walls are double, with an air space of one foot 

 between the inside ceiling and the latticed exterior. The inside 

 dimensions are, 10 feet square with walls 7 feet high. The roof 

 is divided in the middle and the two halves move on pinions giving 

 a maximum opening of 6 feet. The object glass of the telescope, 

 when pointing to the zenith, is about 2 inches below the top line 

 of the walls. 



165 



