38 MICHKi \N ACADEMY OF SCIENCE. 



soil. Along the river ruus the Michigan (Jentral Railroad and the passing 

 of the trains soiiieiinies iii;ikes ii difficult to determine nadirs. The pre- 

 vailing winds are wesicrly. The best seeing is nsualh' in the spring and 

 summer, though there is tine weather also in October, December, and 

 Januaiy. There is considerable dam]>uess. 



The instruments of this observatory were in bad condition when they 

 came into my hands. .It was neeessai-y to take apart and clean the object 

 glasses. Tackles were rigged in the slits of the domes, and the tubes, 

 axes, and bearings of the axes were taken down, and the accumulations 

 of oil and grease remo\-ed. 



2. — Latitude and Lovf/itud(? of the Detroit Observatory. 



As to the latitude no record of an accurate determination can be found. 

 From the discussion which follows of observations of Polaris the latitude 

 can for the present be assumed 



+4.2° 16' 48.8". 



The value +42 IG' 4S.(r as printed in the ephemerides was, I think, an 

 approximate determination. -42° 16' 48", the .0 being finally added by 

 accident. 



The best deterniinrition of longitude is probably that found by connect- 

 ing with Hamilton ('ollege, Clinton, New York. Dr. Briinnow observed at 

 Ann Arbor and Dr. Peters at Clinton. The difference of longitude was 

 found to be 



33m 17.69s. 



Hamilton College had been previously determined with respect to Cam- 

 bridge, and was found to be west of Cambridge 



17m 6.48s. 



Thus the Detroit Observatorv is w^est of Cambridge 



50m 24.21s. 



!See Briinnow's Astronomical Notices, numbers 15 and ;^7. 



Also, Ann Arbor was twice connected with Detroit, and Detroit was 

 connected directly with Cambridge. See pp. 716, 717, 861) of rrufcssional 

 Papers, Corps of Engineers, U. S. A., No. 2-'f, also the Spherical Astronomy 

 of Briinnow, one of the examples under the Method of Least Squares. 

 From these determinations Detroit is west of Cambridge. 



47m 41.17s. 



and Ann Arbor is west of Detroit 



2m 43.10s. 



In the second exchange of longitude signals between Ann Arbor and 

 Detroit apparently there was no telegraph line running to this observa- 

 tory. The signals from Ann Arbor seem to have been sent from a chro- 

 nometer which was carried to the telegraph office. 



3. — The Walker Meridian Circle. 



An investigation of the division errors of the fine circle of this instru- 

 ment was published in Briinnow's Astronomical Notices. I cannot find 

 that anything else has been printed regarding it. 



