252 On the Erroneous Geographical Position of 



reading to 1 0", a level whose divisions indicate 3", and a half) 

 or a third of each division^ may be readily estimated. It is also 

 provided with a telescope having magnifying powers of about 

 twenty and thirty times. To this I had added a chronometer 

 kindly lent me by Mr Robert Bryson, which performed very 

 satisfactorily.* 



The chronometer was compared with the observatory clock at 

 Edinburgh on the 1st August 1836, and was exactly one minute 

 fast of mean time at noon, with a daily rate of three seconds 

 gaining , consequently, the error was 1 minute 12 seconds fast 

 for Edinburgh time, on Friday the 5th of August, the day on 

 which observations were first taken to obtain the latitude and 

 longitude of Broddick Bridge near Jameson's inn in Arran. 



The mean latitude by several series of observations both to the north and 

 south of the zenith, was . . . . 55 35 ' 27' N. 



Longitude by chronometer, 20' 43.6" in time, or . 5 10 54 W. 



The position of Broddick Castle, the seat of the Duke of 

 Hamilton in Arran, inferred from these, will be nearly 

 in latitude . . . . . 55 35 45 N, 



Longitude, 20 '42.8" in time, or 5 10 42 W. 



In like manner, the position of Lamlash church was deter- 

 mined to be in latitude . . . 55 31 56 N. 



Longitude in time 20' 3 1.5" . . . . 2 8 7-5 W. 



These were all the points I had an opportunity of determin- 

 ing by observation directly, and the final results are probably 

 within a few seconds of the truth, both in latitude and longitude. 



By the existing maps, such as they are, and a few angles 

 taken by a pocket sextant, the position of Pladda Light and Kil- 

 mory school were inferred from these. 



Pladda light, Lat. 55 25' 34". North Long. 5 7' 9" W. 



Kilmory school . 55 26 40. North 5 HOW. 



The former agrees very closely with the true position already 

 given, and it is probable the latter is not far from the truth. 



The following are a few heights determined geometrically by 

 the circle above the mean level of the sea : 



Goatfell ...... 2863 feet 



Benoosh ...... 2598 



Muildoun . . . . . . 1138 



* It was with the same chronometer that I made the observations on the 

 solar eclipse which happened on the 15th of May last. 



