90 REPORT— 1881. 



Note on Method of Bechiction. 



1°. Time spent by the sun in every zone of altitude, one degree broad, 

 on each day of the year, is calculated. 



2°. These all added together should give a sum equal to half the year, 

 or 



262,980 minutes. 

 They actually give 



263,020 minutes, 

 being an error of 40 minutes in the whole year. 



3". Supposing the error equally distributed in all the ninety zones ; a 

 correction is made by a multiplier, and the approximate true time spent 

 by the sun in each zone is found. 



4°. These times are then multiplied by the heat-coefficients of each 

 zone, already published (Sheffield). 



5°. Tlie total heat received is represented by 27,03S'425. 



6°. The total heat received, if there were no atmosphere, is 

 40,171-391. 



7°. The heat received at the earth's surface at the equator is there- 

 fore only 07*55 per cent, of that i-ecclved at tho surface of the utmo- 

 sphd'e. 



Fourteenth Report of the Committee, consistinrf o/ Professor Everett, 

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

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

 Professor ED\^'ARD Hull, Dr. Clement Le Neve Foster, Professor 

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

 Mr. GrALLOWAY, jNIr. JoSERii DiCKiNSON, Mr. Gr. F. Deacon, Mr. 

 E. Wethered, and Mr. A. Strahan, appointed for the purpose, 

 of investigating the Rate of Increase of Underground Tempera- 

 ture doivmuarcls in various Localities of Dry Land and under 

 Water, Dratun ^^_p by Professor Everett (Secretary). 



Six observations in the Talargoch Lead Mine, Flintshire, were given in 

 last Report, and another has since been taken at a point distant 400 

 yards to the S.S.W. from Station VI. there mentioned. The depth 

 beneath the surface of the ground is 220 yards, and the position is in a 

 level going west from the engine-shaft. It was 3 yards from the fore- 

 breast, and had only been exposed nine days. The level was dry and 

 there was not much circulation of air. The thermometer (one of the 

 Committee's slow-action instruments) was inserted in a hole 25 inches 

 deep, which was plugged with rag and 12 inches of clay after its inser- 

 tion. It was withdrawn and read on three several occasions, July 19, 23, 

 and 27, and on each occasion the temperature found was 62° Fahr. 



Assuming, as in last year's Report, that 48° is the mean temperature 

 at the surface, this would give an increase of 14° in 660 feet, or of 1° for 

 47 feet. The rock is white limestone with a little chert. 



Comparing this observation with the other six, which exhibited great 

 discordances among themselves, the discordance is still fuT'ther increased, 



