Ordnance Survey of Great Britain and Ireland. 359 



In last year's estimates the sura of 1000^. was taken to enable the di- 

 lector of the survey to extend the trianguiation of England through 

 France to the frontiers of Belgium, so as to form a connection between 

 Uie triangulations of England and Belgium. This operation has been 

 completed. The stations selected to form the connection across the 

 ^'liaunel were St. Peter's Church, between Margate and Ramsgate; Cold- 

 ham, on the high ground north of Folkestone; and Fairlight,a few miles 

 north of Hastings. From these three stations observations were taken 

 to the church at Gravelines, to Mont Couple, near Wissantj and Mont 

 Lambert, near Boulogne. 



From these three last named stations a station raised 74 feet above the 

 level of the ground at Harlettes, between Boulogne and St. Omer, was 

 observed, and then the churches at Cassel and Dunkirk, and then the 

 station at Mont Kemrael, near Ypres, in Belgium. The triangle, Dun- 

 Jiiik, Cassel, and Mont Kemmel, is common to the triangulations of 

 France and Belgium, and is now also made part of the extended triangu- 



I'ts will be highly interesting; but the French officers who were c 



een able last year to take the observations across the Channel, th 

 ii'ison cannot yet be made. They have now, however, returned i 

 >iiiUry to recommence their work, and it is to be hoped they ^ 



theirs with that of Russia; and thus we shall shortly have a connected 

 trianguiation, extending from tlie west of Ireland to the Oural moun- 

 tains, and the means of computing the length of an arc of parallel of 

 about Vo° in len<rth. 



The electric tefegraph now furnishes the means by which the differ- 

 ence of longitude between distant places can be determined with greater 



precision than they could formerly be by the f •-""" "^ "'^ 



ters from one station to another. 



The Astronomer Royal will therefore this ye; 

 ence of longitude between Valentia, in the S.\\. oi ireiaiiu, a.iu luc uu- 

 servatory at Greenwich, by means of the electric telegraph ; and as it 

 ,*iH be necessary for the director of the survey to connect the station se- 

 lected by the Astronomer Royal at Valentia with the triangulat.on of the 

 kingdom, a joint expedition is now about to proceed to Valentia tor this 

 <louble purpose, and to complete the quota of work assigned to us for the 



SHngplvtng of^liTcoraplete map of Ireland in outline, on the scale 

 of one inch to a mile, was finished last year, and the hill features are now 

 being engraved. There are 205 sheets in this map. , ^ ^ , ^ 



The progress of the Cadastral Survey in the north of England and 

 Scotland has been greatly retarded in consequence of the very numerous 

 and extensive surveys which have been made by the Ordnance m 

 .ises connected with the detenses of 



; the differ- 



2 south of England i 



3 kingdom. 



