26 heport— 1880. 



As, however, the experiments are still only in an incipient stage, it is 

 necessary to defer the report of the results attained. 



Under these circumstances the Secretary sus^gests the advisability of 

 the continuation of the Committee on the Lunar Disturbance of Gravity for 

 another year. 



As the plan which the experimenters intend to pursue will involve some 

 masonry work and the use of a good deal of copper for apparatus — an 

 expensive material and difficult to work — it seems likely that future 

 operations may prove expensive. The Secretary, therefore, ventures to 

 suggest that the Association should grant a further sum of 30/. for the 

 purposes of this Committee. 



Thirteenth Report of the GomxiinUtee, consisting o/ Professor Everett, 

 Professor Sir William Thomson, Mr. Gr. J. Symons, Professor 

 Eamsay, Professor GtEIKIE, Mr. J. GtLAISHER, Mr. Pengelly, 

 Professor Edward Hull, Dr. Clement Le Neve Foster, Professor 

 A. S. Herschel, Professor Gr. A. Lebour, Mr. A. B. Wynne, 

 Mr. Gtalloway, Mr. Joseph Dickinson, Mr. Gr. F. Deacon, and 

 Mr. E. Wethered, appointed for the purpose of investigating 

 the Rate of Increase of Underground Temperature dowmvards 

 in various Localities of Dry Land and under Water. Drawn 

 up by Professor Everett {^Secretary). 



Observations have been taken in the Talargoch Lead Mine, Flintshire 

 (between Rhyl and Prestatyn), under the direction of Mr. A. Strahan, of 

 the Geological Survey, and Mr. Walker, Chairman of the Board of Direc- 

 tors of the mine. 



The top of the shaft is 190 feet above the level of the sea, and is at the 

 foot of a hill 500 feet above the sea. The lowest workings are 900 feet 

 below sea-level. The veins run across an angle of Carboniferous Lime- 

 stone, bounded on both sides by faults which throw down coal-measure 

 shale ; and as the faults have a considerable inclination, the lowest work- 

 ings run beneath the shale for a considerable distance. The limestone 

 dips at angles varying from 45° to 55°, and is of two kinds, one white and 

 massive, the other thin bedded black with thin shale partings. 



There are levels at intervals of about 20 yards vertically, in the vein, 

 most of which have been driven for some years ; but all the observations 

 have been taken in newly opened ground. 



They have been taken by boring a hole 24 inches deep at a distance of 

 from 1^ to 5 yards fi'om the fore breast, and either on the same day or 

 the next day inserting one of the Committee's slow-action thermometers, 

 with a foot of plugging consisting of dry rag and clay behind it. After 

 an interval generally of four days the thermometer was taken out and 

 read, then reinserted, and read again about a week later, the difference 

 between the two readings never amounting to so much as half a degree. 



The observations were taken at six different places in the mine, which 

 are designated by the observers Stations I. to VI. ; but in one instance, 

 that of Station II., owing to the swelling of newly exposed shale, the hole 



