Jan. IT, 1877] 



NATURE 



243 



was observed at 2,000 feet ; the water, in each case, having been 

 undisturbed for a month. Supposing these results not to be 

 vitiated by convection, and assuming the mean temperature at 

 the surface to be 50", we hav*> an increase of 29° in 2,000 feet, 

 which is at the rate of 1° in 69 feet. 



Mr. Symons has taken a series of observations at the depth of 

 1,000 feet in the Kentish Town well, with the view of deter- 

 mining whether the temperature changes. The instrument em- 

 ployed is a very large and delicate Phillips' maximum thermo- 

 meter. The following is a list of the observations : — 



The " depth indicated" is shown by a measuring wheel or 

 pulley, over which the wire runs by which the thermometer is 

 raised and lowered, as described, with a diagram, in the 

 Report for 1869. The above table .shows that there is 

 always some stretching, real or apparent, in the interval be- 

 tween lowering the thermometer and raising it again. Recent 

 observations by means of a fixed mark on the wire, have shown 

 that the change is not, in the main, a permanent elongation, but 

 an alternation of length. It is probably due in part to the 

 greater tension which the wire is under in raising than in lower- 

 ing, a circumstance which will cause a temporary difference of 

 length variable with the rapidity of winding up ; also in part to 

 the circumstance that the wire is warmer when it has just left the 

 water than when it is about to be let down. Some portion of 

 the irregularity observed may be due to variations of temperature 

 in that part of the well (210 feet) which contains air. The ob- 

 servations taken as a whole, show that any variations of tempe- 

 rature which occur in this well at the depth of 1,000 feet, are so 

 small as to be comparable with the almost inevitable errors of 

 observation. The observations will be continued at intervals of 

 six months, with additional precautions, and with an excessively 

 slow (specially constructed) non-registering thermometer, in 

 addition to the maximum thermometer hitherto employed. 



Through the kindness of the eminent geologist, M. Delesse, 

 of the Ecole Normale at Paris, observations have been obtained 

 irom the coal-mines of Anzin, in the north of France. They 

 were taken under the direction of M. Marsilly, chief engineer of 

 these mines. Maximum thermometers of the protected Negretti 

 pattern, were inserted in holes bored horizontally to the depth 

 of -6 or -7 of a metre in the sides of shafts which were in process 

 of sinking, and in which there was but little circulation of air. 

 A quarter of an hour was allowed to elapse in each case, after 

 the boring of the hole, before the thermometer was inserted, and 

 the hole plugged. Four different shafts were tried. Those 

 designated as Nos. I., II., III., were in the mine Chabaud La 

 Tour; and No. IV. was in the mine Renard. 



In Shaft I. observations were taken at eight different depths, 

 commencing with the temperature 565° F. at the depth of 38-5 

 metres, and ending with 67 J" F. at 200 5 metres. 



In Shaft II. there were observations at four depths, com- 

 mencing with 55° at 87-3 m., and ending with 634' at 185 m. 



In Shaft III. there were observations at three depths, com- 

 mencing with 56° at 87-8 m., and ending with 624° at 144 m. 



These three shafts, all belonging to the same mine, were very 

 wet, and the temperature of the air in them was il° or 12'^ C. 

 (52° or 54° F.). 



In Shaft IV., which was very dry and had an air temperature of 

 about 15" C. (59'' F.), observations were taken at 6 depths, com- 

 mencing with 7o|° F. at 21 -2 m., and ending with 84° F. at 

 134-8 m. 



The mean rates of increase deduced from these observations 



In Shaft 



I.. 



II., 



III., 



IV., 



F. in 14-4 m., or in 47-2 feet 

 „ 11-5 m., „ 377 „ 

 ,, 8-65 m., „ 28-4 ,, 



8-57 m., „ 28-1 „ 



The observer mentions that in Shaft II. there was at the depth 

 of 90 m. a seam of coal in which heat was generated by oxyda- 

 tion ; but no such remark is made with respect to any of the 

 other shafts, although it is obvious that some disturbing cause 

 has rendered the temperatures in Shaft IV. abnormally high. 

 Possibly the heat generated in boring the holes for the thermo- 

 meters in this shaft (which was dry) has vitiated the observations, 

 the instruments employed being maximum thermometers. Two 

 of the slow non-registering thermometers mentioned in last 

 year's Report have been sent to M. Delesse, to be used for 

 verification. 



The slow-action thermometers are constructed on the following 

 plan : — The bulb is cylindrical and very strong, and is sur- 

 rounded by stearine or tallow, which fills up the space between 

 it and a strong glass shield in which the thermometer is in- 

 closed. The shield is not hermetically sealed (not being in- 

 tended for protection against pressure), but is stopped at the 

 bottom with a cork, so that the thermometer can be taken out 

 and put in again if desired. Stearine and tallow were selected, 

 after trials of several substances, including paraffin- wax, bees'- 

 wax, glue, plaster of Paris, pounded glass, and cotton wool. 

 The thermometers are inclosed in copper cases lined with india- 

 rubber. When placed, without these cases, in water differing 

 10° from their own temperature, they take nearly half a minute 

 to alter by one-tenth of a degree. 



In concluding this Report, your Committee desire to express 

 their regret at the losses which they have sustained by the deaths 

 of Prof. Phillips, Sir Charles Lyell, and Col. Strange, of whose 

 valuable services they have been deprived within the last three 

 years. 



OUR ASTRONOMICAL COLUMN 

 The Rotation of Saturn on his Axis. — On December 7 

 Prof. Hall, of the Naval Observatory at Washington, observed a 

 very white spot on the disc of Saturn, just below the ring. At 

 6h. i8m., Washington mean time, the spot was central, and it 

 was watched from 22h. 40m. sidereal time, to oh. 10m., as it 

 moved across the disc. It was small, very well defined, and 

 from 2" to 3" in diameter. A rough ephemeris of its motion 

 was sent to various observers in" the U. S. , and the observations 

 which have been received are as below. The second column 

 gives the time when the spot was central. 

 Wash- 

 Place. Observer. o - c 



gin 



Washington Hall 



Cambridge A. G. Clark 



Hartford D. W. Edgecomb o 



Poughkeepsie M. Mitchell ... • i 



Albany L. Boss 



Washington Hall o 



,, Eastman 3 



Cambridge A. G. Clark ... -t- 9 



The column o — c gives the residuals when a rotation-time of 

 loh. 15m. is assumed. At Albany, on December 10, the spot 

 was seen, but not until after passing the centre. 



[It will be remarked that the time of rotation, supported by 

 the above observations of a very definite spot, is in close agree- 

 ment with the result obtained by Sir W. Herschel from noting 

 the successive appearances of a belt during the winter of 1793-94, 



