1880.] Northern Sea-horizon. 353 



(2) The Index error of the instrument was marked before and 

 after taking the observations : it seems to have shifted from about 

 50", off the limb, to 40", off the Hmb, i.e. through about 10", while 

 I was at work. 



(3) The Chronometer was set by telegraphic signal, July 27th 

 at Yardo, Aug. 10th and 21st at Christiania, Aug. 26th and 31st at 

 Cambridge, and gave an uniform rate throughout, allowing for 

 change of temperature. 



(4) The ship's course from the time that the Sun would have 

 been visible from behind the cliffs after leaving the harbour of 

 Kielvig, on to the North Cape, and as far as Gjoesvor, is unquestion- 

 able : after that it is a little uncertain, especially after leaving 

 a place named Havosund, but not seriously so. 



(5) The Long, and Lat. throughout are certain. They depend 

 indeed directly on a Norwegian survey of 1848: but this may be 

 taken as proved correct, 1st from the nearness with which the 

 situation of Vardo (another place not very distant), as given in it, 

 corresponds with that obtained by repeated observations of my 

 own ; 2ndly from the near agreement between the position of the 

 North Cape as laid down by the Norwegians, and that given by 

 Mr Bayly, who was sent there in 1769 by the Royal Society. Mr 

 Bayly was accompanied by Mr Dixon, who stationed himself at 

 Hammerfest, about 40 miles to the south-west; and who is also 

 known from having been sent to the Cape of Good Hope in 1761, 

 and at a later date to Pennsylvania, for astronomical objects. Mr 

 Bayly made the place of his own observatory 71" 0' 4''''5 N., 

 26" 1|' E., the chart making it, say, 71" 1', 25" 55' E.; and the North 

 Cape 71" 10' N., 2.5" 49' E., the chart giving 71" 10' N., 25" 46' E. 



(6) The dip, or amount to be subtracted from the altitude 

 above the sea-horizon, owing to the height of the deck and the 

 observer's eye, was carefully ascertained. 



(7) Though there was for some time a thin oblong cloud, about 

 the area of the Sun's disk, near the Sun, nothing in the way of 

 haze or cloud ever obscured the limb observed. 



The observed altitudes, times, &c., &c.,are as follows : sufficient 

 details are given to ascertain the true position of the Sun in every 

 wav in each case. 



2G— 2 



