C77 3 



VIII. Account of a series of observations y made in the summer of 

 the year 1825, for the purpose of determining the difference of 

 meridians of the Royal Observatories of Greenwich and Paris ; 

 drawn up by J. F. W. Herschel, Esq. M. A. Sec. R. S, 

 Communicated by the Board of Longitude. 



Read January is, 1826. 



Operations having been carried on to a considerable extent 

 in France, and other countries on the continent, for the 

 purpose of ascertaining differences of longitude by means of 

 signals, simultaneously observed at different points along a 

 chain of stations ; and the Royal Observatory at Paris, in 

 particular, having been connected in this manner with a 

 number of the most important stations, it was considered 

 desirable by the French government that the Royal Observa- 

 tory at Greenwich should be included in the general design. 

 The British Board of Longitude was accordingly invited to 

 lend its co-operation towards carrying into effect a plan for 

 that purpose ; and the invitation being readily accepted on 

 their part, I was deputed, in conjunction with Capt. Sabine, 

 in the course of the last summer, to direct the practical 

 details of the operation on the British side of the channel, and 

 to make the necessary observations. Every facility was 

 afforded us in making our dispositions, on the part of the 

 different branches of His Majesty's government to which it 

 was found necessary to apply. A detachment of artillery 

 was placed, by his Grace the Duke of Wellington, Master 



