ON THE STRUCTURE OF CARBONIFEROUS-LIMESTONE CORALS. 241 



should occupy small space, be little liable to derangement, capable of being 

 put up in any ordinary apartment not of special construction, and its indica- 

 tions such as any intelligent person could easily interpret and readily note. 

 The Committee are now anxiously considering what instrumental means 

 will best combine these several requisites and advantages, and what stations 

 would be most suitable to select in extending the area of the inquiry. Mean- 

 while the seismometer of the Association, which is the invention of the late 

 Principal Forbes, is kept in proper working order at Comrie, where also the first 

 supplemental indicator will be set up. Principal Forbes's son, Mr. Geo. Forbes, 

 Edinburgh, who has gained some practical acquaintance with earthquake in- 

 struments at Naples, has been taken into their counsels by the Committee, and 

 they have now to request that Mr. Forbes be added to their number. 



(Signed) James Brtce, M.A., LL.D., Convener. 



P.S. — During the Session of the Association at Brighton an earthquake of 

 considerable severity occurred in the Comrie district, of which an account 

 wlU. be given next year. — J. B. 



Fourth Rejjort of the Committee appointed to investigate the Structure 

 of Carboniferous-Litnestone Corals. The Committee consists of 

 James Thomson, F.G.S., and Professor Harkness, F.R.S. 



At the Liverpool Meeting of the British Association the Committee reported 

 that they hoped, by means of a new process, to produce representations of 

 the most delicate internal structures of corals of the Carboniferous series. 

 The necessity of such a process forced itself on the Committee by the circum- 

 stance that none of the existing methods of representing corals reproduced 

 faithfully the details of their internal structure. 



The photographs of the Carboniferous corals exhibited at the Liverpool 

 Meeting represented these details in some of their most delicate forms. 

 This result had been obtained by the transmission of light through their 

 sections ; and subsequent investigations have led us to infer that there are 

 no better means than that of photography for reproducing generic details. 

 Great expense, however, attends this process ; and as it is also a very slow 

 one, experiments have been made in order that the same satisfactory result 

 might be more readily and less expensively obtained. 



At the Edinburgh Meeting they were unable to lay before Section C the 

 same number of results as at the previous Meeting ; but they had so far 

 succeeded as to be able to produce two plates, although they were not so 

 perfect as was desirable : they were, however, sufficiently successful to 

 justify the Committee in asserting that a more simple and less expensive 

 process was available. In the application of this process the Committee 

 have been ably assisted by Mr. Keckie, the artist employed by them in 

 engraving the copper-plates. 



During the past year the investigations of the Committee have been con- 

 tinued with increasing interest. They have now made sections of upwards 

 of 1300 specimens, and have been able to add considerably to this branch of 

 Palaeontology. 



In their Eeport presented to the Liverpool Meeting ninety-two forms were 

 alluded to ; and these presented characters sufficiently distinct to justify thy 



1872. • 8 



