Scientific Intelligence. — Hydrography. 193 



HYDROGRAPHY. 



5. Ice-Islands off the Cape of Good Hope. — A remarkable 

 debacle has taken place this year among the Antarctic ices. A- 

 bout the end of April last, our ships met enormous floating 

 masses of ice, about a hundred leagues from the Cape of Good 

 Hope. The ship Farquharson being in south latitude 39° 45', 

 and 48° 46' long., saw two ice-islands about 150 feet hioh, 

 and about two miles in circumference. Their sides were deep- 

 ly cut by fissures, in which the ice in some places resembled re- 

 fined sugar, in others was not unlike limestone. These islands 

 were surrounded with fields of ice, which appeared to have been 

 broken from these islands. 



6. Colour of Rivers. — The Rhine in its course from the Alps 

 to the Lake Constance is bluish ; after its passage through the 

 green waters of tlie Lake Constance_^it is grass-green ; and after 

 repeated mixture with the rivers and streams of the Vorsch- 

 weitz, Alsace, and the Black Forest, yellowish green. The 

 Main, flowing from the ferruginous rocks and plains of Fran- 

 conia, acquires a reddish yellow colour ; during great degrees 

 of cold, it becomes greenish blue, owing to the deposition of the 

 iron ochre ; and when if it is not coloured yellow, by lono- con- 

 tinued rains, it flows onwards with an umber grey colour. All 

 the rivers, of Old Bavaria, which are formed of waters from 

 lakes and alpine streams on the Iller, Lech, Iser, and the Inn, 

 are bluish green in winter ; in spring grass-green, and in au- 

 tumn pale herb-green. 



MINERALOGY. 



7. Impressions of Gems, ^c. in Siliceous Sinter. — At the hot 

 springs of S. Filippo behind Radicofani, on the borders of the 

 Papal States, siliceous sinter is daily depositing in considerable 

 quantities. Impressions of gems and coins in this siliceous mi- 

 neral, can be obtained in no great length of time, by exposing 

 them to the spray of these springs. 



8. Notice of Magnifcent Rock-Crystals, and rose-coloured 

 Fluor Spar.— Ahout 100 years ago, a great dru.sy cavity, lined 



OCTOBEU — DECEMBER 1829. N 



