480 British Association for the Advancement of Science. 



among the quantities P, Q, R, ..., nor the series for y become 

 a multiple of the primitive equation x m + A x m - l + Bi™" 2 .*. 

 + V = 0. 



[To be continued.] 



LXV. Proceedings of Learned Societies. 



OFFICIAL REPORT OF THE PROCEEDINGS OF THE BRITISH AS- 

 SOCIATION FOR THE ADVANCEMENT OF SCIENCE, AT THE 

 DUBLIN MEETING, AUGUST 1835. 



Communicated by the Council and Secretaries. 



[Continued from p. 411.] 



Notices and Abstracts of Miscellaneous Communications to the Sections, 



continued. 



M 



GEOLOGY AND GEOGRAPHY. 



On the Geological Map of Ireland. By R. J. Griffith. 



R.Griffith presented his Geological Map of Ireland, the result 

 of many years' research and labour, assisted in part by the publi- 

 cations of Weaver, Conybeare, Buckland, and Berger. Mr. Griffith, in 

 pointing out the inaccuracies of existing maps of Ireland, dwelt on 

 the advantages which will be derived from the publication of the Ord- 

 nance maps of Ireland, four counties of which have now appeared. 

 At present great difficulties attend the allocation of geological phe- 

 nomena, which are frequently misplaced in relation to each other, 

 from the necessity of following the defects of the old maps. Mr. Grif- 

 fith, as an example, stated that in Arrowsmith's map, Benwee Head 

 is placed twenty miles north of the parallel of Sligo, though it 

 is actually due west of that town. The remarkable position of 

 the mountain masses was first pointed out. They occur on the 

 margin of the island, and inclose the great central limestone plain ; 

 an arrangement which shortens the courses of the rivers, rising as 

 they do in the higher grounds, and rapidly descending to the sea. 

 The Shannon is an exception, having a course of 140 miles ; but it 

 also is affected by the peculiarity alluded to, its stream falling eighty 

 feet in the first twenty miles of its course, and only eighty feet more 

 in the remaining 120. On the great plain which occupies the centre 

 of the island numerous beds of gravel occur, called Escars, which 

 though constant in direction when considered in reference to small 

 spaces, are variable when the comparison extends over greater 

 limits. Mr. Griffith considers the great bogs as due to these accu- 

 mulations of gravel, which, by damming in the water, facilitate the 

 growth of Sphagnum palustre. Under the bogs are deep deposits of 

 marl, underlaid by clay and gravel, which further support the idea 

 of ancient lakes. The marl was stated to be in one instance forty feet 



occurrence of the expression - was taken into consideration was this, to 



reduce the general equation of the mlh degree to a form which would coincide 

 with Be Moivre's, if m = 5. 



