112 



that year, on Hounslow Heath, in presence of Sir Joseph Banks, 

 then President of the Society, and some of its most distinguished 

 Fellows. 



The principal object which the Government-had then in view, was 

 the connexion of the Observatories of Paris and Greenwich by means 

 of a triangulation, for the purpose of determining the difference of 

 longitude between the two observatories. 



A detailed account of the operations then carried on is given in 

 the first volume of the ' Trigonometrical Survey,' which is a revised 

 account of that which was first published in the ' Philosophical 

 Transactions' for 1785 and three following years. 



At the time when these operations were in progress, the Survey of 

 several counties in the south-east of England, including Kent, Sussex, 

 Surrey, and Hampshire, was also in progress, under the direction of 

 the Master-General of the Ordnance, for the purpose of making 

 military maps of the most important parts of the kingdom in a mili- 

 tary point of view ; and it was then decided to make the triangula- 

 tion which extended from Hounslow to Dover the basis of a trian- 

 gulation for these surveys. 



It is extremely to be regretted that a more enlarged view of the 

 subject had not then been taken, and a proper geometrical projection 

 made for the map of the whole kingdom. As it is, the south-eastern 

 counties were first drawn and published in reference to the meridian 

 of Greenwich, then Devonshire in reference to the meridian of But- 

 terton in that county, and thirdly the northern counties, in reference 

 to the meridian of Delamere in Cheshire ; but there is a large inter- 

 mediate space, the maps of which are made of various sizes to ac- 

 commodate them to the convergence of the meridian. 



In 1799 the Royal Society gave further proof of the interest it 

 took in the progress of the Survey, by lending to the Ordnance its 

 great 3-foot Theodolite, made by Ramsden, for the purpose of expe- 

 diting the work of the Survey ; and although this instrument has 

 been in almost constant use for the last sixty-seven years, during 

 which time it has been placed on the highest church towers and the 

 loftiest mountains in the kingdom, from the Shetlands to the Scilly 

 Islands, it is at this day in perfect working order, and probably one 

 of the very best instruments that was ever made. 



The great Trigonometrical operations of the Survey have been 



