Sept. 12, 1872] 



NATURE 



403 



gentlemen at once in the most obliging manner consented to take 

 observations of temperature in it. An upright Negretti ther- 

 mometer was accordingly furnished; and about the 2'oth of June 

 your Secretary had the pleasure of receiving from them two com- 

 ]ilete sets of observations taken on the 14th and 15th of that 

 month with their own hands, at every looth metre of depth, and 

 also at the bottom of the well, 660 metres deep. 



The observations are given in the subjoined table, in which 

 the third column shows the time that the thermometer was 

 allowed to remain at the depth specified before hauling up and 

 reading. The temperature at whicli the thermometer was set 

 before letting it down is also given in Messrs. Mauget and Lipp- 

 m.ann's report, Init is not here inserted. 



The agreement between the first and second set of observations 

 is remarkably close ; and as the time of leaving the thermometer 

 in the water was about half-an-hour in most of the observations 

 of the first set, and two hours or more in all the observations of 

 the second set, it is obvious that half-an-hour is a sufficient time 

 to give a correct observation. This conclusion is satisfactory 

 both as regards the reliability of the observations themselves, and 

 also as establishing the fact that this pattern of thermometer is 

 not unreasonably slow in its working. The exactness of the 

 agreement also serves to show that the thermometer can be 

 depended on to the tenth of a degree, and that we may Iience- 

 forth use it with confidence. 



Before proceeding to discuss the observations, it will be con- 

 venient to give a few particulars respecting the well, which have 

 been kindlyTurnished by Messrs. Mauget and Lipp-nann. 



It was commenced by the municipal authorities as a masonry 

 well, by the ordinary meihod of diL;ging, until it had reached a 

 depth of 34'5 metres. Ti.e intei.ti ju was to carry it ia this way 

 to the depth of about 135 metres, the estimated depth of the 

 terti.ary strata covering the chalk; but the difficulties and 

 dangers which were encountered, from the want of tenacity in 

 tlie soil {la nature csscntidlcmcnt etmilcuse des terrains), and 

 latterly from the insufficiency of the pumps, rendered it 

 nicess.iry to .abandon this intention; and in May 1S65 the task 

 of completing the well by boring was assigned to Messrs. 

 Degousee and Laurent, the predecessors in business of the gentle- 

 men to whom we are indebted for these observations. A small 

 trill bore (o'2m. in diamet'^r) was commenced, and continued 

 tid January 1S66, by which time the machinery for the heavier 

 work was ready. In order to support the masonry, which 

 showed signs of giving way. it was tubed through its whole 

 length with a tube I Sm. in diameter and 0'02m. thick, cemented 

 externally. From the bottom of this tube, at the depth of 34'5m., 

 a bore i •7m. in diameter was carried to the depth of 6S7m. 

 from the surface of the ground. A second tube i 'sSm. in inter- 

 nal diameter was inserted to the depth of 121 ■6m. , and a third 

 tube of internal diameter 1.39m. was carried down into the 

 ch.ilky marls and the upper portion of the chalk at the depth of 

 I39'i5m. from the surface. From this point downw.ards, the 

 bore has been driven through the chalk, and tubing has been 

 unnecessary, its diameter at the depth of 662m. being still 

 i'35m. 



The thickness of the tertir-Ty strata is 137m., and the elevation 

 of the surface of the ground above sealevel is 4Sm. or 157ft. 



The springs which were met with in the tertiary strata cor- 

 respond to those found in other parts of the basin in which 

 Paris is situated, and have not sufficient strength to spout above 

 the surface of the ground at this elevation. They were en- 

 countered at the depths of I9'2m., 34 'Sm., 86'om. and 97'om., 

 and the water now stands in equilibrium in the central tube at 

 l6'5m. below the suiface of the ground. 



It was not practicable to take ob-ervations of temperature 

 during the regular progress of the boring, but an interruption 

 occurred on the 12th of June, and the tool was not at work 

 from this date till after both sets of observations were finished. 



In reference to this point, Messrs. Mauget and Lippmann, sny, 

 under date April 29, "To obtain the natural temperature, it 

 will be necessary to select a time when the work has been inter- 

 rupted for several days ; for the boring being executed by the 

 fall of a heavy tool upon the bottom of the well, the percussion 

 developes a considerable amount of heat, as we perceive by flie 

 mud (ks bants) which we extract, and which in coming to the 

 surface is found to ha\'e still a temperature of from 48° to go° C . 

 (118° to 194° F.)." In thei-r letter of June 19, containing the 

 report of the observations, they remark : — 



" You will observe that though the water at the bottom of 

 the well is still some degrees above its natural temperature owing 

 to the action of the drill (l>,-fan), the latter has not been in 

 r pel ation since the 1 2th of the month. At a convenient time, 

 we intend to observe the temperature of the mud as it lies at the 

 bottom of the well, immediately after the withdrawal of the 

 drill, when the latter has been working constantly, a temperature 

 which will probably be found to depend upon the hardness of 

 the rock." 



The following table exhibits the successive increments of tem- 

 perature showed in the second series, which purports to be more 

 accurate. 



The last two columns of this table show that the rate of in- 

 crease is about four times as rapid in the last 60m. as in the rest of 

 the well, a circumstance which naturally suggests the explana- 

 tion given by Messrs. Mauget and Lippmann. 1'here are how- 

 ever some difficulties in the way of accepting this view. Com- 

 paring the two sets of observations, one taken on the second and 

 third day after the withdrawal of the tool, and the other on the 

 fifth and sixth day, we have precisely the same temperature at 

 the bottom of the well on both occasions, although the obser- 

 vations were sufficiently precipe to detect a difference of a tenth 

 of a degree where such difference existed. It seems difficult to 

 believe that a temperature 2^. degrees above the normal temper- 

 ature could have remained Dr two days without sensible t-imi- 

 nation. In connection with this question, the apparent cooling 

 to the extent of o°"4 at the depth of 600m. between the first 

 and second observaiion demands attention, and is not very 

 easily explained. 



If the observed temperature at 660m. is to be taken as the 

 normal temperature, the average increase from loom, to that 

 depth is at the rate of 1° F. in 22-im. or in 72'5 ft. If the 

 observed temperature at 600m. in the second series is adopted, 

 the iiicreas-; from loom, to that depth is at the rate of 1° F. in 

 287m. or in 94'2 feet. 



The ob-ervations prepared by Messrs. Mauget and Lipp- 

 mann in the paragr.iph above quoted will be eminently calcu- 

 lated to assist in showing the correct interpretation. 



JNIr. G. A. Lebour, F. G. S. of H.M. Geological .Survey, has 

 furnished observations taken in a bore hole executed at the 

 bottom of South Hetton Collieiy, Durham. The observations 

 were taken by Mr. J. B. Atkinson, a student at the Newcastle 

 College of Physical Science, and appear to have been carefully 

 made. Thanks are also due to the viewer of the colliery, Mr. 

 Matthews, for granting the requisite facilities. 



The hole is 2i inches in diameter, and was bored out of the 

 pumping side of the South Hetton shaft, in order that the bore 

 rods might be the more readily altered. The depth of the shaft 

 is 1,066 feet ; that of the bore hole S63 feet from the bottom of 

 the shaft, or 1,929 feet from the surface of the ground. The 

 section of the boring (not including the shaft) consists of 123 

 alternating beds of shale and sandstone,* with occasional thin 

 seams of coal and some fire clays. The bottom of the boring has 

 reached a very coarse white grit, which is supposed to be the 

 topmost bed of the millstone grit series. 



The bore was dry at the time of its execution ; but has since 

 become filled with wa'er, probably derived from the shaft above 

 it. Strerin.s, in fact, p ur down the shaft, and play about the 

 hole. 



* A complete list of thestr.-ita has been furnished, and will be preserved 

 l<y the Secretary, with a view to future reference if required. 



