VOL. LXV.] PHILOSOPHICAL TRANSACTIONS. 711 



towards the latter. With these 4 poles, the east cairn, and the 2 stations of the 

 observatory, 5 triangles were formed, connecting the 1 stations of the observa- 

 tor)', the relative situation of which to each other would be determine<l as soon 

 as the length of any one of the sides of these triangles was known, either by 

 comparing it with a base measured in the valley below, or with the distance 

 of the 2 cairns settled in that manner. 



I had got sufficient observations of zenith distances of stars with the sector 

 on the south side of the hill by the 15th of August; I prepared therefore for 

 removing the observatory and instruments to the new station on the north side. 

 This was a work of great labour and difficulty, as every thing was carried over 

 the ridge of the hill on men's shoulders, and some of the packages were very 

 weighty ; it employed the labour of 12 men for a week, and was completed on 

 the 26th. A large level area had been cut away, with great labour, here, in the 

 side of the hill, for receiving the observatory, as had before been done on the 

 south side of the hill. A new bothie was also erected, and places for holding 

 the quadrant and transit instrument, as before, adjoining to the observatory. 



The badness of the weather prevented me from beginning my observations 

 with the sector till the 4th of September ; but, that being a clear night, I had 

 a fair opportunity of putting in practice the method of bringing the instru- 

 ment into the meridian by the transits of the stars across the plane of the 

 sector, before-mentioned. The sector being put up with its plane facing the 

 west, and set near the meridian by the variation compass, allowing for the 

 variation, I found, by the transit of Draconis, on the north side of the 

 ijenith, compared with those of x, » and 9 Cygni on the south side, that the 

 instrument deviated 49-^ minutes to the west of the south in azimuth ; which 

 being corrected, by turning the instrument about on its vertical axis, towards 

 the east, by the help of the divisions on the azimuth circle ; I then found by 

 the transit of ri Cephei, compared with that of ir Cygni on the south side, that 

 the instrument deviated 7 minutes to the east of the south in azimuth, which I 

 corrected accordingly. And so near was it brought to the meridian in this 

 manner, that by the most exact comparison of the transits of several stars on the 

 7th and 8th instant, it appeared to be only 2 minutes out of the meridian, and 

 that to the east of the south ; which small error I also attempted to correct ; 

 the instrument rested 1 minute out of the position which I intended to give it, 

 owing to the difficulty of turning it about to such great nicety, and so I let it 

 remain. 



It was indeed a most fortunate circumstance, that I thus got the instrument 

 so near the meridian by the very first night's observations, those of September 

 4th ; for the badness of the weather in the day prevented me from getting a 

 meridian line by the sun till the 15th. Had I therefore been obliged to wait 



