VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 237 



brevity as possible, inserted a narrative of each year's operations. This will be 

 found however to extend only to the 1st part, or that containing the particulars of 

 the survey in which the great instrument alone was used. The remaining contents 

 of this portion of the work, are necessarily confined to the angles of the principal 

 and secondary triangles, with the calculations of their sides, in feet ; and likewise 

 such data as have no connection with the computations of latitudes and longitudes. 

 The 2d part contains an account of a survey carried on in Kent, in the years 

 1795 and 1796, with the small instrument, for completing a map of the eastern 

 and southern parts of that county, for the use of the Board of Ordnance, and the 

 military commanders on the coast. In the 1st part will be found an article, for 

 which we are indebted to Dr. Maskelyne, the Astronomer Royal. It contains his 

 demonstration of M. de Lambre's formula, in the Connoissance des Temps of 1793, 

 for reducing a distance on the sphere to any great circle near it, or the contrary. 

 The practical rule thence derived, for reducing the angles in the plane of the hori- 

 zon, to those formed by the chords, is very useful, and will considerably abridge 

 the trouble which must necessarily arise in computing the chord corrections by any 

 former method. 



Some angles are next registered as taken at the best stations in Devonshire, and 

 other points in the west of England, in the year 179 5 - The survey then extends 

 farther westwards in the next year 17 96. . It is here observed that, to make obser- 

 vations for the purpose of hereafter determining the longitude and latitude of the 

 Lizard, was a principal object in this year's operations ; and as this headland seems 

 to offer itself as very convenient for a station, it will be right to assign the reasons 

 for not having chosen one upon it. 



As no other spot but Hensbarrow Beacon could be found in that part of Corn- 

 wall proper for a station, it became necessary to fix on the Deadman, or Dodman, 

 for another point in the series. From this place no part of the land within 4 miles 

 of the Lizard can be seen, as the high ground about Black Head, which is to the 

 eastward of the latter, is nearly in a line between them, and is also much higher 

 than both. It will be perceived however, that no evil can result from the want of 

 such a station, as the light-houses and the naval signal-staff at the Lizard, have 

 been intersected from several stations. The precise spot on which Mr. Bradley 

 made his observations in the year 1769, for ascertaining the longitude and latitude 

 of this headland, was pointed out by the person having the care of the light-houses, 

 who well remembered the common particulars relating to his operations : such 

 measurements were made from the light-houses to this spot, as may enable us, at 

 a future period, to compare the results from the data afforded by the trigonometri- 

 cal operation, with those deduced from the astronomical observations made by the 

 above gentleman. It may be also mentioned, that angles were at the same time 

 taken at the western light-house and signal-staff, for the purpose of finding the 

 situation of the Lizard Point. 



