684 GEODESY AND PENDULUM EXPERIMENTS. 



6. Measuring the Advance of the Glacier in Franz-Joseph- 

 Fiord. (R. COPELAND.) 



Two signal stations were taken on the glacier, and their posi- 

 tions determined with reference to two points on the side of the 

 glacier, 80 metres apart, in a line parallel to the motion of the 

 glacier. 



The motion of the marks was measured on August 11, after 19 

 hours, from 4 p.m. to 11 a.m., and again on August 12, after 

 another interval of 18 hours, from 11 a.m. to 5 a.m. the next 

 morning. 



From these observations the daily advance of the glacier was 

 found to be 0- 164 + 0*019 metres. 



7. Measurement of Motion of Glacier by Dr. Hayes. 

 (Smithson Contrib., vol. xv.) 



In the autumn of 1860 Dr. Hayes made a survey of glacier in the 

 neighbourhood of Port Foulke, the end of it being about two miles 

 from the sea. A base line was measured along its axis, and bear- 

 ings taken to fixed objects on the mountain on each side. After 

 eight months the measurements indicated a motion of 94 feet. 



On the interesting subject of the motion of the Swiss glaciers, 

 reference may be made to papers of Prof. Forbes, in the Edinburgh 

 New Philosophical Journal (Oct. 1842), who discovered that the 

 central portion of a glacier moves more rapidly than the sides, 

 and that a glacier is continually advancing ; also to the works of 

 De Saussure, about the same period, in the " Comptes Rendus," 

 and especially to the experiments of Dr. Tyndall, on the motion 

 of the Mer de Glace. (Tyndall's Glaciers of the Alps, p. 275.) 



VI.—ATMOSPHERIC REFRACTION AT LOW 

 TEMPERATURES. 



1. Appendix to Sir John Ross's North-west Passage. 



" Captain Scoresby gives some extraordinary instances of both 

 land and ships seen at immense distances, and on our first voyage 

 it is recorded that Cape Clarence was seen from the deck at the 

 distance of 120 miles, the ship being at that time 2° of latitude 

 south of the cape. The most remarkable circumstance which 

 occurred was the uneven current of refraction raising^ an inter- 

 mediate body (an iceberg or island) above the more distant land, 

 which at the time of no refraction was considerably higher." 



2. Observations at Port Bowen. (Parry's Third Voyage, &c.) 



(Page 56.) The amount of atmospheric refraction at low tem- 

 peratures was the subject which, next to magnetism, appeared the 



