from a level at the depth of 398 feet below ground, and the surface of the water in it is 399 feet down the shaft, or 797 feet below the surface of the ground. There are pumps in the shaft, but they had been stationary for more than 24 hours before the observations were made. Immediately after the observations they were started, and when they had been working for some time the temperature of the water lifted was found to be 65°.2. They draw their water at a depth of 957 feet below the surface of the ground. The following were the observations:

The thermometer could not be lowered beyond 857 feet without risk of losing it, by getting fast in the wooden framework with which the pumps were secured. Mr. Burns thinks that some of the temperatures here recorded are too low, from the index being shaken down by reason of the impediments presented by the upper portions of the framework. The surface of the ground over this shaft is about 300 feet higher than over Gin-Hill shaft. If we allow 1° for this increase of height, and call the temperature of the surface of the ground 44°-3, as against 45°3 at Gin Hill, we have, by comparison with the observed temperature 65°-7 at the depth of 857 feet, an increase of 21°.4 in 857 feet, or 1° in 40 feet.

On the 6th July Mr. Ridley took observations in another sump or underground shaft at Slitt mine, Weardale. This shaft is sunk from the lowest level in the working, and had been standing full of water during the five months which had elapsed since it was sunk. The only source of disturbance was a little water running along the level across the top of the shaft, so as to enter the shaft (so to speak) on one side and leave it on the other. This may affect the temperature at 3 feet, but could scarcely affect the temperature at 53 feet, which may be regarded as very reliable. The following are the observations :

Mr. Burns says "the surface-temperature at Slitt mine will be nearly the same as that at Gin-Hill shaft, judging from their relative elevations, aspects, and 'exposure to the winds." Assuming it then to be 45°.3, and reckoning the temperature at 660 feet as 65°, we have an increase downwards of 190.7 in 660 feet, or 1° in 33.5 feet. The only datum that seems doubtful here is the surface-temperature. If, instead of 45°-3, it be assumed 44°.3 460.3, it gives an increase of 1o in

as

1460-3'

31.91 135.3

feet.

Mr. Ridley has also taken observations in Breckon-Hill shaft, which is near the river Allen, about 1 mile from Gin-Hill shaft, and at an elevation

At the

not much above the bottom of the valley, but 1174 feet above sea-level. It was sunk some years ago, and has since stood nearly full of water. time of the observations the surface of the water was 24 feet down the The following are the observations taken in this shaft on June

shaft. 13th:

These observations were taken early in the morning, when the air and springs were so cold as to allow the maximum thermometer to be cooled below the temperature of the shaft. In order to test more thoroughly the apparent uniformity of temperature from 100 feet down to 350 feet, Mr. Ridley took a second series of observations, extending from the 22nd to the 27th June. In these observations the thermometer was lowered in a tin case filled with water colder than that of the shaft. The thermometer was supported within the case in a vertical position by a wooden frame, and prevented from shaking about. It was allowed to remain at each depth several hours, was then lifted, and read with all possible care. The following are the observations thus obtained :

Depth under ground.

Length of immersion.

10 40
11 20

Temperature before
immersion.

Temperature after immersion.

TITT

11 40

12 20

13 40

10 25

Here the temperature is even more uniform than in the first series. As to the causes of this uniformity, Mr. Burns remarks that the shaft is not connected with any working, but is cut through solid strata. It is a few yards to the east of the Allen, while, in the bed of that stream, and making a great spread on the west side of the valley, is a bed of limestone nearly 70 feet thick, and dipping at an angle of about 10° to the east. The top of this limestone was cut in the shaft about 40 feet down, which occasioned a great influx of water into the shaft, and drained a strong spring on the other side of the river.

It will be observed that the chief difference between the two sets of observations is just at the place where this limestone was cut. The second set were taken after and during much rain, and the first set after a week of very little rain. It appears probable that the difference of temperature at this

depth was due to the difference of temperature of the surface-water which soaked in through the limestone in the two cases. As regards the temperatures at depths exceeding 200 feet, it would appear that, in times of comparative drought (as in the first set), the heat of the soil at the greater depths has time to produce a little augmentation in the temperature of the water before it soaks away.

This shaft is obviously not adapted for giving any information as to the rate of increase downwards. Collecting the best determinations from the other shafts we have :

Mr. Burns considers that little or no weight should be attached to the first of these determinations, as a pumping-engine was working in a neighbouring shaft communicating with it at the time when the observations were taken. The jump of 2° in descending from 340 to 390 feet also renders the interpretation of these observations difficult.

The closeness of the temperatures in the other two shafts, at depths differing by about 200 feet, suggests the idea that they are both fed by the same spring, and that the temperatures indicated are the temperature of the origin of the spring slightly modified by the different temperatures of the strata through which it has passed; but their positions appear to render this impossible.

Mr. Burns's opinion from all the observations is that the mean rate of increase downwards at Allenheads is about 1° in 35 feet; but this cannot at present be held as proved.

The strata consist mainly of alternate beds of sandstone and shale, with a few beds of limestone intermixed. In Slitt mine there is also a bed of basalt 158 feet thick, overlying the vein of fluor-spar in which the workings are carried on, the workings being 55 feet down in this vein.

Preparations are being made for taking observations in the dry part of the mines, by making shallow bores at different levels, inserting the thermometer, plugging up the hole for a few days, and then reading.

Another gentleman connected with H.M. Geological Survey, Mr. R. L. Jack, has taken observations in a bore at Crawriggs, Kirkintilloch, near Glasgow. They were taken on the 29th November 1870, the temperature of the air being 34°. The surface of the water in the bore was 6 feet below the surface of the ground, the latter being 200 feet above sea-level. The following were the observations:

:

A few feet below 350 feet an obstruction in the bore prevented further

observations; but the bore continues for about 70 feet further. We have here a total increase of 4° in 300 feet, which is at the rate of 1o in 75 feet; but the intermediate steps are so irregular that not much weight can be attached to this determination.

The Secretary has corresponded with the Smithsonian Institution respecting the great bore at St. Louis, which was described in last year's Report, and also respecting the Hoosac Tunnel which passes under a mountain and will be 43 miles long, but the correspondence has not yet led to any definite result.

It was stated in last Report that application had been made to General Helmersen, of the Mining College, St. Petersburg, for information regarding the temperature of a very deep bore in course of sinking at Moscow, as well as regarding underground temperatures in Russia generally. A long delay occurred, owing to the General being absent from home for seven months, and not receiving the communication till his return; but shortly after his return he dispatched a very polite answer, from which the following passages are extracted:" We have an artesian well in St. Petersburg, bored in the Lower Silurian strata. At the depth of 656 English feet this well stops at the granite, a granite which perfectly resembles that of Finland. The lowest portion of these Silurian strata is merely a degraded granite, a grit combined with débris of felspar. About 353,000 hectolitres of water flow from the well per diem, and this water issues with a constant temperature of 9°.8 Reaumur. You are doubtless aware of the existence of a series of observations on the temperature of the soil at the bottom of a well which was sunk in the town of Yakoutsk in Eastern Siberia. This well has shown us that the soil of Siberia, at least in this part of its great extent, is frozen to a depth of 540 English feet. The mean temperature of Yakoutsk is -8°.2 R. At the depth of 100 feet the temperature of the soil was found to be -5°.2. From this depth to the bottom the temperature increased at the rate of 1° R. for every 117 feet; whence it would follow that the soil at Yakoutsk is frozen to the depth of about 700 feet.

It appears to me a very interesting circumstance that, according to accounts just received by the Academy of Sciences from Baron Maydel, traveller in the country of the Tchukchees [des Tschouktschi], there are found in those regions layers of ice, quite pure, alternating with sand and clay. The interesting letter of the Baron will shortly be printed in the publications of the Academy. It was in making excavations in search of mammoths that Maydel made this discovery."

If we assume the temperature of the surface of the soil at St. Petersburg to be 39°-17 F., which, according to Herschel's Meteorology,' is the mean temperature of the air at the Magnetic and Meteorological Observatory, and if we take the temperature of the water as that of the bottom of the well, we have an increase downwards of 14°.88 F. in 656 feet, which is at the rate of 1° F. in 44.1 feet. If, on the other hand, we suppose the surface of the ground to be 4° F. warmer than the air (and the difference at Yakoutsk appears to be greater than this), we deduce an increase at the rate of 1° F. in 60 feet.

The rate of increase at Yakoutsk from the depth of 100 feet to the bottom of the frozen well at 540 feet is given above by General Helmersen as 1o R. in 117 feet. This is 1° F. in 52 feet.

An account of the Yakoutsk well is given in Comptes Rendus,' tome vi. 1838, p. 501, in an extract from a letter by Erman (fils), who visited Yakoutsk when the well had attained a depth of 50 feet. He gives the tem

perature at this depth from his own observations, and the temperatures at 77, 119, and 382 feet from the subsequent observations of the merchant to whom the well belonged. His figures differ very materially from those given above; but it may fairly be presumed that General Helmersen's account is the more accurate.

Before the receipt of General Helmersen's letter, the following communication respecting the Moscow boring had been received by the Secretary from Mons. N. Lubimoff, Professor of Natural Philosophy in the University of Moscow.

"December, 1870.

"DEAR SIR,-I beg your pardon for not having replied sooner to your letter. I am sorry to say that the information which I can now communicate is very deficient. The great bore of Moscow is not yet terminated, and the experiments on temperature which have been made hitherto are but of a preliminary kind. It was in the hope of renewing the measurements under more satisfactory conditions that I delayed my answer; but as certain circumstances did not permit me to resume the observations, which are therefore deferred to the spring of 1871, I must restrict myself to describing the old ones. "These were made, on my commission, by M. Schiller, B.A., in April 1869. The bore was then about 994 feet deep, and, from 56 feet to the bottom, full of water. A mercury thermometer of a peculiar kind was constructed, on an idea of my own. It consisted of a capillary tube of thick glass, terminating below in a large reservoir; at the upper end a funnel-like piece was adjusted, into which the mercury flowed off as soon as the temperature rose above a certain value [sketch annexed]. The whole was placed within a closed case, which was plunged to a chosen depth into the bore, and reversed by means of a special arrangement. It was then brought again to the right position and drawn up to the surface, a portion of mercury having flowed away. Here the thermometer was plunged into a water-bath, the temperature of which was so regulated that the mercury attained the end of the capillary tube; this was then the temperature required.

"The measurements were made at the depths of 175, 350, 525, 700, 875, and 994 feet. From 350 feet to the bottom the temperature throughout the bore was found to be nearly constant, namely 10°.1 C., with deviations of +0°.1. The temperatures of the upper parts of the bore were not quite precisely ascertained, the chief attention being given, in these first experiments, to the deeper parts. The air-temperature at the surface for the time 23 April April to varied between +7°-5 and -1°.9 C. 5 May

17

29

"As soon as the boring is completed, and the present impediments removed from the bore, the observations will be resumed, and perhaps some new methods will be applied for the sake of verification, though the above described apparatus, previously tried, seemed to give very exact results.

"I shall be very glad to communicate to you, as soon as possible, the results of the new experiments. As to underground temperatures for Russia in general, there is, so far as I know, no place where regular and trustworthy observations have been made [should be made in original] except the Central Physical Observatory at St. Petersburg, the results of which are published by Dr. Wild, Director of the establishment, in his printed Annual Reports."

From the sketch annexed to the description in Professor Lubimoff's letter, it appears that the enlargement at the open end of the capillary tube is quite sudden, and not likely to retain any mercury when inverted. The idea of error from this cause may therefore be dismissed; but the instrument is en