86 



NA TURE 



Nov. 27, 1884 



reservoir should always be about 1 5 lbs. above that in the 

 train-pipe, so that when the brakes are being released by 

 increasing the pressure in the train-pipe direct from the 

 main reservoir, the triple valves are certain to act, on 

 account of the extra 15 lbs. pressure in the train-pipe 

 above the pressure in the small reservoirs. 



On moving the handle of the driver's valve further in 

 the same direction, or into the position for applying the 

 brakes, all connection between the main reservoir and 

 the train-pipe is cut off, at the same time that the train- 

 pipe is put in connection with the atmosphere, through an 

 exhaust port ; by this means the pressure in the train- 

 pipe can be reduced to any degree to apply the brake. 

 All brake-cylinders on vehicles are fitted with a release- 

 valve, so that, should the brake be applied when the 

 engine is not attached, the air can be discharged from 

 the brake-cylinder, through the release-valve, by pulling 

 a wire attached to the valve. 



All vehicles now fitted with this brake have cocks at 

 each end of the train-pipe, so that, should any change 

 have to be made in the train, the coupling or uncoupling 

 of vehicles is easily accomplished without the brake 

 automatically applying itself. 



It is easy to see that this brake is automatic in its 

 action, for should the train-pipe or flexible couplings be 

 injured by accident, or the train part into two or more 

 portions, the compressed air will escape from the train- 

 pipe, and the brake will apply itself. In all guards' vans 

 is placed a cock in connection with the train-pipe, so that, 

 should the guard observe anything wrong with the train, 

 or receive a signal from a passenger, he can instanta- 

 neously apply the brake by opening the cock and 

 discharging the air from the train-pipe. 



The Westinghouse automatic brake is at present the 

 only one which really includes all the qualities in the 

 Hoard of Trade requirements for continuous brakes, and 

 perhaps it will not be out of place to state the require- 

 ments of the Board of Trade. 



(1) The brakes to be efficient in stopping trains, instan- 

 taneous in their action, capable of being applied without 

 difficulty by engine-drivers and guards. 



(2) In cases of accident, to be instantaneously self- 

 acting. 



(3) The brakes to be put on and taken off (with facility) 

 on the engine and every vehicle of a train. 



(4) The brakes to be used in daily working. 



(5) The material employed to be of a durable character, 

 so as to be easily maintained and kept in order. 



On looking through the Board of Trade returns on 

 continuous brakes for the six months ending June 30, one 

 sees that over two-thirds of the failures of the Westing- 

 house automatic are due to burst hose pipes alone, and 

 therefore not failures of the brake itself, but of faulty 

 inspection and bad material. We would like to hear of 

 experiments being made with a stronger and more durable 

 material, so as to resist the destructive action of the oil 

 and tallow, of which such a large quantity is used on 

 railways. Could this improvement be effected, we are 

 convinced the number of miles run per failure would im- 

 mediately vastly increase, leaving the automatic vacuum 

 brake far behind. Of failures of the triple valve to act 

 we find fifteen reports, causing a very trifling delay to the 

 trains. The air-pump is reported with eleven failures, and 

 the driver's brake-valve has no failures recorded against 

 it. When we consider the enormous mileage of 15,506,447 

 miles run by trains fitted with the Westinghouse auto- 

 matic for the six months ending June 30, we cannot help 

 being astonished at the freedom from failure of the dif- 

 ferent parts, and the general efficiency of the apparatus. 



Much has been written about the failure of the 

 simple vacuum brake in the Penistone accident on the 

 Manchester, Sheffield, and Lincolnshire Railway, the 

 disaster being attributed by some to the brake failure 

 alone. Certainly, had the train been fitted with the 



Westinghouse automatic, the brake power on each 

 vehicle would have remained intact, no matter how many 

 couplings broke : but at the same time the fact seems to 

 have been overlooked that the train had no permanent 

 way to run on, since the engine bioke up the chairs as it 

 advanced, and the question remains, How would the 

 train have been affected, having nearly all the wheels 

 locked by the brake, and running over sleepers alone ? 

 Perhaps the train would not have travelled so far before 

 going over the embankment ; but we think the disaster 

 would have been equally serious, each vehicle becoming 

 detached by the sudden application of the brake, the 

 couplings breaking on account of the violent jerks in 

 passing over the sleepers, the curve tending to throw the 

 vehicles over the embankment. As an example of the 

 life-saving qualities of an automatic brake in an accident, 

 we think the Penistone disaster would have been a poor 

 specimen. 



The question of automatic versus simple brakes, both 

 pressure and vacuum, is now fairly before the public, and 

 the policy of the Board of Trade seems more apparent every 

 day. It would not be wise on their part to enforce the 

 adoption of any particular patent brake, for a better one 

 may any day be discovered, but the Board may fairly 

 insist that their conditions as to the qualities of any brake 

 adopted by any Company should be complied with, and, 

 if necessary, enforced by Act of Parliament. 



THE GALVANOMETER OF D'ARSONVAL 

 AND DEPREZ 



GALVANOMETERS of innumerable kinds abound, 

 and each form has some special merit which renders 

 it useful for certain restricted services. The old astatic 

 instrument of Nobili is still preferred by many to the 

 more modern mirror galvanometer of Sir W. Thomson 

 because it requires no lamp, and can be used without 

 darkening the room. The tangent galvanometer still 

 holds its own in the testing-room for simple tests ; and 

 the lineman's detector is still indispensable on the score 

 of its portability. For commercial purposes, where strong 

 currents and steady potentials have to be measured, the 

 newer ampere-meters and volt-meters have displaced the 

 older forms of instrument. But still there is no best 

 galvanometer of universal adaptability, even the Siemens 

 " universal " galvanometer being too clumsy to meet with 

 general favour. 



For the purposes of the private laboratory a galvano- 

 meter is desired which shall be sensitive, yet accurate in 

 its indications, capable of being used for measuring cur- 

 rents of all kinds, weak and strong, and of measuring 

 differences of potential from the thousandth of a volt to 

 a thousand volts. It ought to be capable of being used 

 in broad daylight ; of being rapidly read off; and it ought 

 also to be independent of external magnetic disturbances. 

 The annoyances which arise from the last two causes 

 when working with sensitive galvanometers are only too 

 well known. The needle of the instrument once deflected 

 continues to oscillate perhaps for half a minute, perhaps 

 longer, causing vexatious delays, and when perhaps it has 

 settled down at last to zero, some person in the next room 

 moves a piece of iron — a poker, a penknife, or some other 

 magnetic object — causing the zero of the instrument to 

 change. An aperiodic dead-beat instrument, not subject 

 to external magnetic forces, would be a boon indeed. 



A galvanometer which, without being absolutely perfect, 

 goes very near to fulfilling these desirable conditions has 

 lately been put into the hands of electricians by M. Car- 

 pentier, of Paris, successor to the well-known Ruhmkorff. 

 It is the invention of M. Marcel Deprez as modified and 

 improved by Dr. d'Arsonval. The many novel features 

 which it presents would of themselves justify its descrip- 

 tion in the p 1 jes of NATURE : and the general excellence 



