1841.1 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



241 



Fig. 10, M is the Electric Detector, for detecting injury caused to the wires, 

 either by contact with the pipe or with eacli other, fracture, or water. 



)«, is a small battery ; 1 m, 2 m, are " feelers," in connection with the 

 battery auci detector. Whenever tliese feelers touch each other, an electric 

 current passes from the battery and influences the index of the detector M, 

 by turning it on its axis. J J are iron boxes which occur at short intervals 

 along the line, each fitted with a screw Ud, and so connected as to render 

 them continuous with the tube C. The terminations of each length of wire 

 rope one introduced into the box and each wire screwed with its fellow to a 

 piece of wood (itted to the bottom of the box, so that the wire marked 1 is 

 continuous throughout its length and always connected by the screw 1, by 

 which it can be recognized at every box along the Une. The openings by 

 which the wires enter the box are hermetically scaled with composition ; but 

 a small tube passing through the box admits of a free communication of air 

 from a distant reservoir. Suppose wire 1 to have become in partial contact 

 with the tube, either by the metals touching or the presence of water : upon 

 opening the box at which the wire is to be proved, tlie screw I must be taken 

 out, and the feeler 1 m brought in contact with one end of the separated 

 wires, the other feeler being kept in contact with the pipe. If this portion 

 of the conducting wire is sound, the detector needle remains stationary ; but 

 upon removing the feeler, 1 m, to the other liberated end of wire, the detector 

 index moves on its a.\is, and indicates on the graduated scale the degree of 



Fig. 11. 



contact existing between that portion of the wire and the tube. Supposing 

 the experiment to he tried again at the next box, and the contact proved to 

 lie between the two boxes, the intervening faulty portion of wire is exchanged 

 for the sound wire marked 0, (which is a spare wire introduced by such re- 

 pairs) by this means the wire 1 is again restored to soundness ; it is obvious 

 that dirterent portions of the spare wire, 0, may thus be employed to repair 

 a damaged wire, at numerous short intervals along the line, without render- 

 ing it necessary to disturl) the line generally ; tlie minutest changes in the 

 insulation of the wires from dampness, &c., can be detected by this valuable 

 instrument, and corrected by blowing through the pipe a draught of drj' air 

 from the reservoir. 



When a length of wire-rope has to be removed, in consequence of acci- 

 dental injury, tlie connecting screws in the boxes at each end of the length 

 are taken out, and one end of the wires to he removed is bound to the eud 

 of a fresh length of wire-rope conveniently wound upon a drum. The further 

 end of the faulty length is then drawn out of the tube and wound upon an 

 empty drum, as the new rope gradually takes its place. The screws again 

 unite the ends of the wires, and the line is restored. The faulty length of 

 wire, after undergoing examination and repair, is again fitted for use. 



Each wire is separately covered with cotton and India-rubber solution, and 

 the set of wires made into a rope, which is passed through a hot resinous 

 vainish before being introduced into the tubes. 



Fig. 11. Air-pressure apparatus, employed for excluding 

 water from the tube, when carried underground ; and for 

 giving notice of defects in the tubing. 



H is an air-pressure apparatus, or air reservoir, of convenient 

 size, charged witli dry air to any pressure. 1 A is a pressure 

 balance, in tlie form of a lever ; 2 A a valve communicating, by 

 a minute opening, between the reservoir H and the protecting 

 tube C. Suppose it to be found desirable to keep the interior 

 of the tube under a pressure of two or three pounds (that lieing 

 calculated as sufficient to exclude the greatest pressure of water 

 to which the tuljc is Uable), the balance 1 h must then be 

 loaded to that amount ; on any escape of air taking place from 

 the tube, the lever arm, 1 h, would descend and open the valve 

 1 //, till the high-pressure reservoir had increased the pressure 

 of the tube, which by raising the pressure-balance 1 A, would 

 close the valve 2 //. A barometer, L, may indicate the change 

 of pressure either in the reservoir or tube. The reservoir is 

 supplied by an air-pump, when nearly exhausted by any leak- 

 age, which, under the light pressure of two or three povmds, 

 should be very trifling. Should the barometer, however, indi- 

 cate a sudden escape of air, attention must immediately be di- 

 rected to the proving-boxes J, which occur at short intervals 

 along the line. 



In or nc^r the box, conveniently connected with the tube, 

 is a three-way stop-cock, to the pipe of which a portable ba- 

 rometer or detector, L, can immediately be applied. When 

 the tube is faulty, upon turning the cock in one direction, the 

 pressure on the barometer will remain steady, but in the other 

 direction it will rapidly diminish, from the escape of the air. 

 By proceeding with a similar experiment at other proving- 

 boxes, the two boxes will be readily ascertained between which 

 the escape of the air takes place ; when the tube lying between 

 the last proved points must be carefully examined to discover 

 the faulty part. 



THE .4.RTESIAN BORLN'G AT PARIS. 



In the Journal for April last, we gave an account of the successful ope- 

 rations in sinking the Artesian well at Crenelle ; we are now enabled to 

 furnish some farther detail of the geological formation through which the 

 boring passed, from the observations of M. Mulot given in the Revue Gene, 

 rale, together with some additional information as to the size of the bore, 

 and the geological character of the circumjacent country. 



Table of the depths of the strata measured from the surface in metres and 

 reduced to English feet. 

 Metres. Feet. 



10 33 Alluvial formation, the former bed of the Seine. 



41 134 Plastic clay and quartzose sand. 



White chalk with black flints. 

 Gray chalk and flint. 



Gray chalk, very hard, with layers of micaceous clay. 

 Blue clay, green clay, micaceous black clay, with fossils 



and iron pyrites. 

 .\rgilIaceous green sand. 

 Beyond here the sand continues and has not as yet been quite explored, it 

 is in this stratum that the water is obtained. 



The boring was commenced at a diameter of 0-51 metres (20 inches) and 

 diminished by degrees as the tubes descended, the first four columns of tub- 

 ing diminishing as just observed, to the depth of 145 metres (576 feet) ; at 

 this point the diameter was 0-31 centira. (12 inches). 



547 



1794 



A 5th column of tubing goes down to 350 metres (1148 feet), with a dia- 

 meter of 0-26 (10 inches.) 



A 6th to 410 metres (1345 feet) diameter 0-21 (8} inches.) 



A 7th to 540 metres (1771 feet) diameter, 0'17 (6} inches). 



The last 7 metres (23 feet) are not tubed. 



The fixing of the ascensional tube is always an operation very important 

 and delicate, and will on this occasion in particular present serious difficul- 

 ties. Indeed one would suppose that it was almost impossible to lower per- 

 pendicularly a tube 547 metres (1794 feet) high into the earth, but from M. 

 Mulot's skill, of which he has given so many proofs during the work, we are 

 completely assured of its final success. 



The quality and kind of metal which composes the ascensional tube have 

 been studied by persons interested in the construction of the well ; for 

 many tubes of this kind have been constructed of wrouglit iron, and have not 

 answered the expectations of the parties interested. A remarkable instance 

 may be cited which happened at Saint Cyr, near Tours, at Dr. Bretonncau's 

 artesian well. The water there rises from the sand beneath the chalk, and 

 was tubed with iron, yet every successive year the quantity of water was 

 sensibly diminished, and at last gave only an insignificant supply. M. Bre- 

 tonneau caused the tubing to be drawn up, and although it had at least a 

 thickness of 8 millim. (^ of an inch) and was well preserved, yet at the joints 

 of each pipe there was one, and sometimes several circular holes two and 

 even three centim. diameter, (about an inch diameter,) of which the edges 

 were perfectly sharp, as though they had been cut out by a pah- of 

 nippers. This phenomena was probably due to an electro-chemical action, 



2 L 



