THE JURASSIC DEPOSITS WHICH UNDERLIE LONDON. 729 
tube, which was buried for its whole length (5 ft.) in a bed of sand 
10 ft. in thickness, which had been washed in to the bottom of the 
bore-hole. To endeavour to prevent any heat being lost by convec- 
tive disturbance, the bore-hole was plugged with cement and sand 
for several feet above the layer of washed-in sand. The thermo- 
meter was left at the bottom for 3 days (viz. from noon, Saturday 
J une 7th, to noon, Tuesday June 10th), when it was hauled up and 
found again to haye registered a temperature of 754° Fahr,; the 
temperature of the air at the surface, when the thermometer was 
lowered, being 54° Fahr., and when brought to surface 57° Fahr. 
Taking an assumed surface-temperature of 50° Fahr., and com- 
paring it with 754 Fahr. at the depth of 1337 ft., the result indicates 
an increase of temperature at the rate of 1° Fahr. for every 52°43 ft. 
in depth. 
Lhe thermometer used for the above trials was a Negretti’s maxi- 
mum, kindly sent to the author for the purpose by Prof. Everett, 
Secretary to the Underground Temperature Committee of the British 
Association. 
Lable of Trials. 
Time Thermom. 
Trial Temperature of Air ay t 
Wate: p i emperature 
No. id at Surface. fee a registered. 
1 | March 25th, 1884 51° Fahy. 1; hours 753° Fahr. 
2 | March 3lst, 1884 53° Fahr. 53 hours 754° Fahr. 
34] tom || 540 to 57° Fabr. | 72hours | 753° Fah. 
In conclusion, I may add that the boring, which is still in progress, 
had, at the date of this paper going to press, Oct. 15th, 1884, attained 
the depth of 1409 ft., being 107 ft. deeper than that of the deepest 
well or bore-hole hitherto sunk in the London Basin. The deepest 
well and bore-hole before this was sunk was that at Kentish Town, 
which reached to the depth of 1302 ft. from the surface. 
When, however, we take the mean of high- and low-water as a 
datum (O.D.), and compare the relative depths, then it will be found 
that the bore-hole at Richmond has reached the depth of 274 ft. below 
that of Kentish Town (see fig. 2, p. 760). C. H. 
Il. Generat REMARKS oN THE GEOLOGICAL BEARINGS OF THE 
UNDERTAKING. 
My attention was first directed to this interesting section some 
time after the Gault had been reached in the boring, and since then 
every facility has been kindly afforded me by Mr. 8. C. Homer- 
