ON THE RATE OF INCREASE OF UNDERGROUND TEMPERATURE. 93 
Seventeenth Report of the Committee, consisting of Professor 
Everett, Professor Sir W. THomson, Mr. G. J. Symons, Sir A. C. 
Ramsay, Dr. A. Gerkrz, Mr. J. GLAISHER, Mr. PENGELLY, Pre- 
fessor Epwarpd Hu.., Professor Prestwica, Dr. C. LE NEVE 
Foster, Professor A. S. HERSCHEL, Professor G. A. LEBour, Mr. 
GaLLoway, Mr. JoserpH Dickinson, Mr. G. F. Deacon, Mr. E. 
WETHERED, and Mr. A. STRAHAN, appointed for the purpose of 
investigating the Rate of Increase of Underground Temperature 
downwards in various Localities of Dry Land and under 
Water. Drawn wp by Professor EVERETT (Secretary). 
Tux present Report is for the two years which have elapsed since the 
summer of 1883. . 
Observations have been taken in a deep bore at Richmond, Surrey, 
by Mr. Collett Homersham, M.Inst.C.E., F.G.S. It is on the premises of 
‘the Richmond Vestry Waterworks, on the right bank of the Thames, 
and about 33 yards from high-water mark. The surface is 17 feet above 
Ordnance datum. 
The upper part consists of a well 253 feet deep, with an internal 
diameter of 7 feet at top and 5 feet at bottom, which was sunk in 1876 
for the purpose of supplying water to the town of Richmond, and carried 
down to the chalk. From the bottom of the well a 24-inch bore-hole 
was sunk to the total depth of 434 feet, thus penetrating 181 feet into 
the chalk. This portion of the work was completed in 1877. Above 
the chalk were tertiaries, consisting of 160 feet of London clay, 60 feet 
of the Woolwich and Reading beds, and some underlying sands. The 
water yielded at this stage was about 160 gallons a minute, and when 
not depressed by pumping was able to rise 4 or 5 feet above the surface. 
Its ordinary level, owing to pumping, was about 130 feet lower. 
In 1881 the Richmond Vestry determined to carry the bore-hole to a 
much greater depth, and the deepening has been executed under the 
direction of Mr. Homersham’s father, who is consulting engineer to the 
Vestry. 
The existing bore-hole was first enlarged and straightened, to enable 
a line of cast-iron pipes, with an internal diameter of 164 inches, having 
the lower end driven water-tight into the chalk at a depth of 438 feet, 
to be carried up to the surface. The annular space surrounding this pipe 
served to furnish an uncontaminated supply of water to the town during 
the deepening. 
The total thickness of the chalk was 671 feet. Below this was the 
upper greensand, 16 feet thick; then the gault clay, 2014 feet thick; 
‘then 10 feet of a sandy rock, and a thin layer of phosphatic nodules. 
Down to this point the new boring had yielded no water. Then followed 
a bed 87} feet thick, consisting mainly of hard oolitic limestone. Two 
small springs of water were met with in this bed at the depths of 1,203 
and 1,210 feet, the yield at the surface being 1} gallons a minute, with 
power to rise in a tube and overflow 49 feet above the ground. A partial 
analysis of this limestone rock showed it to contain 2'4 per cent. of 
