92 Rev. C. P. N. Wilton on the Geology 



hand was removed and the eye opened, a black spot, the size 

 of a sixpence, was seen in the axis of vision. 



It is from pressures on the retina that those floating masses 

 of light are produced, which appear in particular states of in- 

 disposition. In affections of the stomach the pressure of the 

 blood-vessels upon the retina is shown in the dark by a faint 

 blue light, floating before the eye and passing off at one side. 

 As the pressure increases, the blue light becomes green^ then 

 yellow, and sometimes even red, all these colours being occa- 

 sionally seen at the edge of the luminous mass. 



The preceding observations on the influence of dilatation 

 in making the retina insensible to light, render it extremely 

 probable that the disease in that membrane, called Amaurosis, 

 may sometimes arise from a general distention of the eyeball, 

 arising from a superabundance of the fluids which it incloses. 

 If this be the case, the removal of the pressure might be ef- 

 fected by puncturing the eyeball (where it can be done with 

 safety), and letting out a portion of the aqueous humour. How 

 far such an operation would be effectual when the disease has 

 been of long standing can be determined only by experi- 

 ment. 



XX. A Sketch of the Geology of Six Miles of the South-east 

 Line of the Coast ofNewcastle in Australia; — ixith a Notice 

 of three Burning Cliffs on that Coast. By the Rev. Charles 

 Pleydell Neall Wilton, M.A. of St. John's College 

 Cambridge, Felloiv of the Cambridge Philosophical Society, 

 and Chaplain of Newcastle* . 



''I ""HE whole line of the cliffs from the point [a) to (b) in the 

 -*• accompanying figure, affords a fine field for the operations 

 of the geologist ; and though in some parts the abruptness of 

 the rocks, which project at their base into the sea, and in 

 others the stupendous masses, which have from time to time 

 (by the violent winds of the south-east gales, which prevail on 

 this coast), been detached from the overhanging precipices, 

 and been hurled to the bottom, impede the naturalist in his 

 progress, — yet is his toil amply rewarded by the interesting 

 results of his several investigations. 



The height of the cliffs in general varies from about 100 

 to 300 feet, and their surface towards the sea presents in some 

 places three and in others ttao parallel horizontal beds of coal, 

 of the independent formation (with sometimes an occasional 

 dip), having alternating layers of shale, breccia, more or less 

 compact chert, sandstone, millstone-grit, clay-stone, slaty clay, 

 clay-ironstone, and thin laminae of ironstone divided into 



* Cominunicatcd by the Author. 



