Proceedings of the British Association. 118 



explaining the recession of this cataract. It is well known that the 

 river Niagara flows upon a bed of limestone from which it projects 

 itself, and that this rock is supported by a strong bed of friable shale 

 upwards of seventy feet thick. The moisture arising from the screen 

 of water, the current of wind behind it, and the concussion, loosen 

 and remove the shale, and the superincumbent limestone, losing its 

 support, falls down. In this manner the cataract has receded at 

 least six miles from the Queenston heights. Mr. Featherstonhaugh 

 expressed an opinion that this operation of excavating long channels 

 of rivers, as in the instance especially of the Mississippi, may be con- 

 sidered in the class of providential arrangments, since by it the lakes, 

 swamps, and immense marecageous surfaces become drained, and 

 rendered salubrious and productive habitations for man. There were 

 many other interesting points brought forward in this paper, of 

 which we have only room for this abstract. 



1 On the physical character and geology of Norfolk Island,' by 

 Capt. Maconochie, R.N., K.H. — The group, of which Norfolk 

 Island is the principal, is situate in lat. 29° 2' S., and 168° 2' E. 

 long., 900 miles E.N.E. of Sydney, and 1,350 N.E. from Cape 

 Pillar, in Van Diemen's Land. Norfolk and Philip Islands, the largest 

 of the group, are about 6 miles distant from each other ; about a 

 dozen others, the Nepean and Bird Islands, are little more than dry 

 rocks distributed about them. Norfolk Island is not quite 5 miles 

 long, with a medium breadth of about 2 J miles ; and its superficies 

 is said to be 8,960 acres ; its greatest elevation is the double summit 

 of Mount Pitt, 1,050 feet high ; its sea- front is high and precipitous, 

 presenting cliffs 200 and 250 feet in height, and the small streams 

 which occupy the ravines in winter, fall, in cascades 30 or 50 feet 

 high, into the sea. Philip Island is about \\ mile long, with an 

 average breadth of f . Its most elevated point is probably two or 

 three hundred feet less than that of Norfolk Island. It is every- 

 where precipitous, furrowed by deep channels, and densely wooded, 

 though the timber is small and of little value. Both these islands 

 are masses of porphyry, much decomposed on the surface ; boulders 

 of compact greenstone are abundant in both islands, especially in 

 the fields and watercourses of Norfolk Island, where they are em- 

 ployed as building materials. They are also found imbedded in 



