253 REPORT— 1873. 



Sixth Report of the Committee, consisting of Prof. Everett^ Sir W. 

 Thomson, F.R.S., Sir Charles Lyell, Bart., F.R.S., Prof. J. Clerk 

 Maxwell, F.R.S., Prof. Phillips, F.R.S., G. J. Symons, F.M.S., 

 Prof Ramsay, F.R.S., Prof. A. Geikie, F.R.S., James Glaisher, 

 F.R.S., Rev. Dr. Graham, George Maw, F.G.S., W. Pengelly, 

 FR.S., S. J. Mackie, F.G.S., Prof. Hull, F.R.S., Prof. Ansted, 

 F.R.S., and J. Prestwich, F.R.S., apiJointed for the purpose of 

 investigating the Rate of Increase of Underground Temperature 

 downwards in various Localities of Dry Land and under Water. 

 Drawn up by Prof. Everett, D.C.L., Secretary. 



In last year's Eeport a very interesting series of observations was recorded, 

 taken in the great well of La Chapelle at Paris, by Messrs. Maugct and 

 Lijipmann. The temperature recorded showed a tolerably regular increase, 

 at the average rate of 1° Falir. for every 94 feet, down to the depth of 600 

 metres. In comparing the temperature at this depth with that at the bottom 

 of the well, 60 metres lower, an increase about four times as rapid was 

 found. 



The Secretary has since visited the well, and witnessed, with the advan- 

 tage of Mons. Mauget's explanations, the very interesting operation of 

 boring. From subsequent calculation, based on the data thus obtained, he 

 has been led to concvir in the explanation originally given by Messrs. Mauget 

 and Lippmann of the abnormal increase in the last 60 metres. 



The Avell has in its lower portion an internal diameter of 1-35 metre, and 

 consequently a sectional area of 1'43 square metre. The boring is executed by 

 means of a kind of chisel, whose edge is a convex arc of a circle. This chisel, 

 with its frame, weighs 3000 kilogrammes. It is lifted and dropped by means 

 of a series of iron rods screwed together, so as to form one rod 660 metres 

 long. The arrangements are such that, when the chisel has been lifted -4 

 of a metre from the bottom, it becomes automatically released, and falls back 

 through this distance. The rod is then lowered after it through an equal or 

 slightly greater distance ; and, by another self-acting arrangement, the tool 

 becomes again attached ready for a new lift. The rods are hung from one 

 end of the beam of an engine, which takes two seconds to rise, and the same 

 time to descend. The tool is therefore droj^ped fifteen times in a minute. 



When this work has been going on uninterruptedly for several hours, the 

 tool is raised above ground, and a cylindrical vessel, with a number of valves 

 in its bottom, is lowered for extracting the mud and chips which have been 

 produced by the operation above described. As three hours are required either 

 for raising or lowering, a considerable portion of the twenty-four hours in each 

 day is occupied by these subsidiary operations ; and for some time previous 

 to the observations detailed in last year's Eeport, the time actually spent in 

 using the chisel was about 100 hours per week. 



Hence we have the following calculation for the heat developed by the 

 action of the tool. The weight of the tool in air is 3000 kilogrammes. Its 

 weight in water may be assumed to be ^ of this. Hence the work done in 

 raising it through -4 of a metre is 1050 kilogrammetres. Heat equivalent to 

 this is generated in its fall ; and as 424 kilogrammetres of work are equiva- 

 lent to one kilogramme degree Centigrade, we have 2-48 kilogramme 

 degrees Centigrade, or 4-46 kilogramme degrees Fahr. as the product of each 

 fall of the tool ; that is to say, one kilogramme of water woiild be raised in 

 temperature 4°-46 Fahr. by the heat produced in one fall. The number of 



