1835.] the Advancement of Science. 195 



as they occur in Wales, while Mr. Sedgwick has investigated 

 those of Cumberland. 



According to Mr. Murchison, the older secondary rocks 

 of Wales, which he, for the sake of convenience, denomi- 

 nates the Silurian group, may be classed under three divi- 

 sions, each of them containing its peculiar organic remains, 

 and consisting of a great variety of rocks. 



In the descending series, and departing from the old red 

 sand-stone, we have the Ludlow rocks, attaining to a thick- 

 ness of 2,000 feet, consisting of crystalline argillaceous 

 lime-stones, with flags and shales. 



These rocks are followed by the Wenlock group, con- 

 sisting also of limestones and shales. These are succeeded 

 by what Mr. Murchison has denominated the Caradoc 

 group, a series of rocks similar to the preceding, and 

 attaining to a very great thickness. 



These formations, however, appear to be newer than the 

 Cumbrian rocks which have been investigated by Mr. Sedg- 

 wick, and which he also divides into three subordinate 

 groups, all of which are included under the name of Cum- 

 brian rocks. The first, or upper, is the Plinlimmon group ; 

 The second, or Snowden group ; and, thirdly, a lower group. 

 The details on this last series of rocks were rather meagre, 

 but we have no doubt that ample information will shortly 

 be laid before the public. 



Chemistry and Minei^alogy. — Monday^ \Oth August. Dr. 

 Thomas Thomson, President. Dr. Dalton, and Dr. 

 Barker, Vice-Presidents. Dr. Apjohn, and Mr. John- 

 ston, Secretaries. Committee, — Mr. Davy, Mr. Vernon 

 Harcourt, Dr. Daubeny, Mr. Graham, Mr. Connell, 

 Dr. R. D. Thomson, Mr. Kane, Mr. Ferguson, Mr. 

 ScANLAN, Dr. Geoghegan, &c. 



The Secretary presented to the Section printed copies of 

 tables, exhibiting at a single view, the most important 

 properties of simple and compound bodies, for defraying the 

 expenses of the printing of which, £10 had been allocated 

 at the last Meeting of the Association. 



1. A paper was then read by Mr. Davy, upon the subject 

 of the corrosion of iron by sea water. The observations had 

 particular reference to the injury sustained by the iron of 



o2 



