AT INTERVALS OP" TEN SECONDS. 



The following observations were made, pursuant to arrangement with Prof. A. D. Baehe, 

 Superintendent U. S. Coast Survey. Comparisons at short intervals had previously been mad<* 

 (in 1840) by the observatories at Cambridge, (Mass.) Philadelphia, and Washington, and at a 

 later period by himself and Prof. Lloyd at Dublin, but were inconclusive on both occasions, em 

 Prof. Bache supposed, because of separation of the continents at the last series, and dissimilarity 

 of the instruments in both. When suggesting the present series, Prof. Bache intended to 

 cause corresponding observations to be made by parties in Oregon, and at one station on the 

 eastern coast of the United States ; and it was presumed that the Toronto observatory, and a 

 party of the Mexican boundary commission, in California, would also cooperate. 



The times agreed upon were the first day of each month, unless it fell on Sunday, and in 

 such case on the second day of the month, from 17 hre - to 18 hre - Gottingen, civ41 reckoning, and the 

 observations were to be made during that hour at the shortest possible intervals. 



JULY i, 1850. 



