UNDERGRDU>"D TEMPERATURE. 107 



Undergroimd Temperature. — Tiventieth Report of the Committee, con- 

 sisting of Professor J. D. Everett, Professor Lord Kelvin, 

 Mr. Gr. J. Symons, Sir A. Geikie, Mr. J. Glaisher, Professor 

 Edward Hull, Professor J. Prestwich, Dr. C. Le Neve Foster, 

 Professor A. S. Herschel, Professor G. A. Lebour, Mr. A. B. 

 Wynne, Mr. W. Galloway, 'Mr. Joseph Dickinson, Mr. G. P. 

 Deacon, Mr. E. AVethered, Mr. A. Strahan, and Professor 

 MiCHiE Smith. (Brawn np hij Professor Everett, Secretary.) 



The Committee were appointed for the purpose of investigating the rate 

 of increase of underground temperature downwards in various localities of 

 dry land and under water. 



The nineteenth Report contained the results of observations taken in. 

 1891 by Mr. Hallock, of the Smithsonian Institution, at depths extend- 

 ing to 4,402 feet in a nearly dry well at Wheeling, Virginia. 



Mr. Hallock, who now dates from Columbia College, New York, has 

 recently furnished the Secretary with printed copies of a paper, contributed 

 by him to the American Association for the Advancement of Science last 

 year, containing further observations iu the well, made at the expense of 

 the U.S. Geological Survey. 



When the observations of 1891 were finished, an oak plug was driven 

 into the top of the casing to protect the hole. In July 1893 the plug was 

 withdrawn, and the well, instead of being dry as before, was found to be 

 full of fresh water to within 40 feet of the top. This water is believed to 

 have leaked in at the lower end of the innermost casing — that is, at 

 1,570 feet below the surface. 



By means of inverted Negretti maximum thermometers, protected 

 against pressure by sealing them in stout glass tubes, careful observations 

 were taken at various depths from 1,586 feet to 3,196 feet, two thermo- 

 meters being employed to check one another at each depth. The results 

 were practically identical with those obtained two years previously, when 

 the well was full of air, the greatest certain difference being only one-fifth 

 of a degree. An obstruction at 3,200 feet prevented observation at 

 greater depths ; but this obstruction will probably be removed, the well 

 pumped dry, and the drilling continued. 



In making the observations, four thermometers were lowered at a time, 

 two of them being in an iroii bucket 3 feet long and 3 inches in diameter 

 at the end of tlie wire, and the other two in an open wire frame 260 feet 

 from the end of the wire, the diameter of the bore being just under 

 5 inches. 



The temperatures at 103 feet, 206 feet, and 300 feet were also observed 

 with suitable thermometers, the temperature at 103 feet being 52°'53, 

 which is 1°'2 higher than the true temperature of the soil at that depth, 

 as determined by other observations in the immediate neighbourhood. 



The smallness of the disturbance of temperature by convective circu- 

 lation in this well, both when dry and when filled with water, is very 

 remarkable, and renders the well specially suitable for determinations of 

 the increase of temperature downwards. 



The Committee have to record with deep regret the loss of their 

 valuable member, Mr. Pengelly. 



