Roi/al Irish Academy, 385 



which are observed when common light is incident^ the intrusion oF 

 a new ring, &c. But there is one curious appearance which he 

 does not find described by any former author. It is this. Through 

 the last twenty or thirty degrees of incidence the first dark ring, 

 surrounding the central spot which is comparatively bright, remains 

 constantly of the same magnitude ; although the other rings, like 

 Newton's rings formed between two glass lenses, dilate greatly with 

 the obliquity of incidence. This appearance was observed at the 

 same time by Professor Lloyd. The explanation is easy. It de- 

 pends simply on this circumstance, (which is evident from the 

 table,) that the angle 180° — 5, at these oblique incidences, is nearly 

 proportional to cos i. 



As to the index of refraction in metals, the author conjectures 



that it is equal to . 



cos p^ ^ 



Rev. Robert Gage exhibited specimens of Coal and Ironstone, 

 recently found in Rathlin Island, on the north coast of Ireland. 



Nov. 30, 18.^(;. — Sir William Betham exhibited to the Academy a 

 specimen of the ancient brazen ring money, found in the county of 

 Monaghan, and also a piece of cast iron, found with many others, in 

 boxes, on board a vessel wrecked on the coast of Cork last summer. 

 This vessel was bound to Africa, where it is stated the pieces in 

 question pass for money. They are so similar in shape and size to 

 the ancient specimens, that there can be no reasonable doubt of the 

 identity of their uses ; and thus the theory advanced in the paper 

 referred to is strongly confirmed. 



Sir William Betham also read an extract of a letter from a friend, 

 in which it was stated, that gold rings, exactly formed like those 

 found in the Irish bogs, — that is, of gold wire turned into the form 

 of rings, but not united at the ends, — pass current at this moment 

 as money in Nubia and Sennaar. 



The Dean of St. Patrick's exhibited two bronze specimens of the 

 first-mentioned articles found in Italy, one of which was encrusted 

 with crystals of carbonate of lime. 



The following papers were read : 1. "On the Affinity of the 

 Hiberno-Celtic and Phoenician Languages." By Sir William 

 Betham, M.R.I.A., Secretary of Foreign Correspondence. An ab- 

 stract of this paper appears in the " Proceedings " of the Academy, 

 No. L 



2. '• On the Propagation of Light in Uncrystallized Media." By 

 the Rev. H. Lloyd, F.R.S., M.R.I. A., Professor of Natural Philo- 

 sophy in the University of Dublin. 



The objects of the author have been — 1. to simplify and to deve- 

 lop that part of M. Cauchy's theory which relates* to the propaga- 

 tion of light in an aethereal medium of uniform density; 2. to ex- 

 tend the same theory to the case of the aether inclosed in uncry- 

 stallized substances, taking into account the action of the material 

 molecules. 



Some of the simplifications adopted in the first part of these in- 



Third Series. Vol. 10. No. 62. May 1837. 3 D 



