J.S47. 



THE CIVIL ENGINI:ER and ARCHITECT'S JOURNAL. 



177 



snow-storm was falling at one end of tlie line, and clear weather ex- 

 isted at tlie other. On another occasion a continned stream of elec- 

 tricity was ob-^erved to pass between two points at a break in the 

 wire,' presenting the appearance of a gas-light almost extinguished. 

 A constant effect of this kind indicates a constant accession of electri- 

 city at one part of the wire, and a constant discharge at the other. 



3. The natnral electrici'y of the wire of the telegraph is liable to be 

 disturbed bv the ordinary electrical induction of a distant cloud. Sup- 

 pose a thnn'der-cloud, driven by the wind in such a direction as to 

 cioss one end of the line of the telegraph at the elevation, say of a 

 mile ; during the whole time of the approach of the cloud to the point 

 of its pathclirectly above the wire, the repulsion of the redundant 

 electricity with which it is charged would cimstantly drive more and 

 more of the natural electricity of the wire to the further end of the 

 line, and would thus give rise to a current. When the cloud arrived at 

 the point nearest to the wire, the current would cease for a moment; 

 and as the repulsion gradually diminished by the receding of the cloud, 

 the natural electricity id the wire would gradually return to its nor- 

 leal state, giving rise to a current in an opposite direction. If the 

 cloud were driven by the wind parallel to the line of the telegraph, a 

 current would be produced towards each end of the wire, and these 

 would constantly vary in intensity with the tliU'erent positions of the 

 cloud. Although currents produced in this way may be too feeble to 

 set in motion tlie marking apparatus, yet they may have sufficient 

 power to influence the action of the current of the battery so as to in- 

 terfi-re with the perfect operation of the machine. 



(To be conlhiucd.J 



LOCOMOTIVE SLIDE VALVES. 



Sir — The following is a scheme for relieving the slide valves of a 

 locomotive engine from the great pressure which is upon them (in the 

 ordinary valves^. It is thus: 



WATER-BALANCE WINDING MACHINE. 



Weare indebted for llie fol'.ovving description and engravings to the Mining Jonrnal. 



In this sectional view, the slide will be seen to have two ports a, a' 

 connected with each other, and of equal area to those on the cylinder 

 face, b, b'; c is a plate placed on the back of the valve, and kept there by 

 means of a strong spring, which should be tested, to stand the amount 

 of pressure there would be on a space equal to the area of the two 

 ports n, a'; s is a steam-way, through which the steam is admitted, 

 passing from thence through the ports into the cylinder. The pres- 

 sure on the space between the ports is neutralised by the strip f, to 

 which I think there can be no objection, as it would only open and 

 shut the steam-way simultaneously with the steam ports in the cylin- 

 der; therefore, the supply of steam would be as regular as were it 

 full open during the entire travel of the valve. The exhaust is formed 

 through the chamber R, and the blast-pipe P. The lap of the valve 

 is of course at the will of the engineer. Hoping that the scheme will 

 meet with your approbation and insertion in your next, 

 I am, Sir, your's, very respectively, 



F, A. BUCKNALL. 



Bintol,May 22, 1847. 



Description. — A AAA, the pits; BB B B, plate-iron water-tanks i 

 C C, two wagons ; D D D D D D, part of the rails, and the bridge 

 across the top of the tanks; E E E, different views of the cross con- 

 necting the tanks and wire ropes; F F, water-pipes, provided with 

 valves, for fil ing the tanks — to be opened and shut bv levers, under 

 the command of the attendant; G G G G G, the walling, or steaniug, 



of the pits ; H H,exit valves, at the bottom of the tanks. The large 

 wheel has a groove to receive the rope, or chain, as the case may be, 

 and furnished with a brake, to regulate the motion and gripe tight, as 

 the wagons reach the proper places for pushing off and on. It will be 

 necessary to attach a rope (or chain) to the bottom of the tanks, simi- 

 lar to that annexed, in order to keep up the equilibrium through the 

 whole depth of the pit; for, where the ground is favourable, one 

 elliptical pit will be a saving in sinking and steaning, as well as in the 

 size of the wheel, wliich may be proportionably less. — The upright 

 pipe, seen behind the wheel, may be surmounted by a cistern, to relieve 

 the pipes and joints from the shock occasioned by suddenly checking 

 the momentum of the water-current along the horizontal pipes. 



It should be understood, that guide-rods, though not showD, are 

 necessary to keep the tanks steady. 



It is now 20 years since 1 erected one of these machines, which has 

 oeen in constant work ever since, and is still raising 500 tons, from li 

 depth of 50 yards, in 12 hours. 



Cokford, May 8. 



John Walkikshaw, 



