247 



The author then alluded to the map of Egypt, which was 

 made during the period it was under the dominion of the 

 French republic, and which received from Buonaparte all 

 that protection and assistance, which so much distinguished 

 him on all occasions regarding the advancement of the works 

 of science. This map was engraved on fifty-three sheets of 

 copper, and the names are engraved both in Arabic and 

 French. 



After this introductory account of the rise and present 

 state of the topographical Art, Mr. Bald proceeded to the 

 details connected with the survey of Mayo. 



The instruments used in this survey, were a seven-inch 

 theodolite ; two five-inch theodolites, by Troughton ; a 

 small theodolite, by Dollond ; and also a five-inch one by 

 the same artist. In taking the levels over the bogs, two of 

 Troughton's best levels were used. The barometers were 

 made by Mr. Thomas Jones, of London. There were also 

 two plain tables, a chain for measuring base lines, a sextant 

 four inches radius, and two sextants, each ten inches radius, 

 divided to ten seconds for observing altitudes, one of which 

 was made by Troughton. 



The proceedings of the geometrical details of the survey 

 were then given, and the mode of describing the rise and 

 fall of the ground, which was shaded on the map with 

 a depth of colour corresponding to the sines of the angles of 

 inclination. The irregularities of surface were simply de- 

 lineated by hatching lines, drawn in the direction of the de- 

 clivities, forming a series of normals, perpendicular to the 

 horizontal lines of equal level. 



Dr. Smith read a paper (by Lieutenant Newenham, 

 R. N.), " on a Tumulus or Barrow, near Rush, County of 

 Dublin." 



The barrow, called Knocklea, or the Giant's Hill, is 

 tuated on the edge of the cliff, about midway between the 



