ON THE EXPLORATION OF THE FERMANAGH CAVES. 183 



There can be no doubt that the surest way to bring any point of a 

 boring to its original temperature is to fill up the bore, and reduce it as 

 nearly as possible to its original condition. Several instruments have 

 been contrived which, when buried in the earth, with wires coming from 

 them to the surface, admit of having their temperature observed by 

 electrical means. 



One of these is Siemens' resistance thermometer, another is Wheat- 

 stone's telegraphic thermometer, of which a description will be found in 

 the Report of the Dundee Meeting of the British Association ; another 

 is Becquerel's thermo-electric apparatus, which has been employed by its 

 inventor and his son and grandson for some forty years. It is described 

 in the following terms in the first report of this Committee (1868) : — 



" The thermo-electric method might also be followed with great 

 advantage. Two wires, one of iron and the other of copper, insulated by 

 gutta-percha or some other covering, as in submarine cables, and 

 connected at their ends, might be let down, so as to bring their lower 

 junction to the point where the temperature is to be taken, their upper 

 junction being immersed in a basin of water, and the circuit completed 

 through a galvanometer. The temperature of the water in the basin 

 might then be altered till the galvanometer gave zero indication." 



Sir Wm. Thomson now adds the recommendation, that, in carrying 

 out this method, the two wires, each well covered with gutta-percha, 

 should be twisted together ; that the wires should be stout and as homo- 

 geneous as possible throughout, and that a piece of stout copper tube 

 should be attached to the lower junction, this tube being uncovered and 

 in close contact with the earth all round, its purpose being to ensure that 

 the junction takes the proper temperature. 



It would probably be desirable, in filling up the bore, to mix clay 

 with the original material, to render it watertight, for it would be 

 impossible to render the filling of the bore as compact as the surrounding 

 rock. 



Several pairs of wires would be buried in the same bore, with their 

 lower junctions at different carefully measured depths. 



The upper junctions would be kept in a room provided with a steady 

 table for a mirror-galvanometer. 



Report of the Committee, consisting of the Rev. Dr. Haughton, Prof. 

 Leith Adams, Prof. Barrett, Mr. Hardman, and Dr. Macalister, 

 appointed for the purpose of Exploring the Fermanagh Caves. 

 Drawn up by Mr. Thomas Plunkett, Enniskillen, for Dr. Mac- 

 alister, Secretary of the Committee. 



Probably there is no locality in Ireland where there are so many 

 interesting caves found as in the region of Knockmore, in Fermanagh. 

 Fifteen of these caves have been explored during the past three years, 

 every one of which yielded memorials of man, and were no doubt used by 

 savage tribes as dwelling-places. 



A. — The first cave explored this year was partially excavated last year. 

 It penetrates a deep escarpment on the eastern side of a rocky hill, and 



