OCTOUER 25, 1906] 



NA TURE 



^i7 



coupled eng-ine with a leading? bof^ie, haviii^^ an eif^lil- 

 wheeled boj^ie tender. The coaches were not of 

 excessive length, the longfest being 48 feet, and all 

 were on bogies; the engine was one of the company's 

 oMial modern express type, and although the boiler 

 is mounted higher than was formerly the practice, 

 the train was well calculated to run safely round 

 curves under usual conditions : yet it was a curve that 

 caused the accident. In saying this we are not 

 vcrhallv in agreement with Major Pringle's report or 

 with the verdict of the coroner's jury at the inquest 

 (in the unfortunate victims, both of which .ittribute 

 the accident to excessive speed. No doubt the speed 

 at which the curve was taken was too high, but if 

 the curve had not been so sharp the speed would 

 have been perfectly safe; in fact, it w:is the curve 

 which was the abnormal feature, the speed being 

 ordinary for ordinary conditions. It may seem like 

 splitting hairs to cavil over terms in this manner, 

 hut the matter has greater significance than may 

 appear. If we allow the accident to have been due 

 simply to speed, then the railway authorities have 

 done all that they can do when they order drivers — 

 as they always have done — to reduce speed to within 

 safe limits; but if it is stated that the accident was 

 due to excessive curvature of track, then the company 

 will appear not to have done all that is possible until 

 they flatten the curve. Whether the danger warrants 

 the expenditure is another matter, but we may re- 

 member that so long as drivers are human and liable 

 to err, the chance of disaster is always present whilst 

 such an abnormal curve e.xists on a main line over 

 which express trains run ; in other words, if the 

 .Salisbury curve did not exist accident from the same 

 cause would be impossible. 



.Speed is always a doubtful point in the elucidation 

 of the cause of accident, but there is no doubt, from 

 the evidence at the inquest and the Board of Trade 

 inquiry, that the train was travelling very greatly in 

 excess of the thirty miles an hour laid down by the 

 regulations as safe for the curve immediately to the 

 east of Salisburv station. One witness estimated the 

 speed to have been as high as seventy miles an hour, 

 and Major Pringle considers that possiblv this may not 

 have been an extravagant estimate. When the engine 

 and tender left the line it came into violent contact 

 with a milk train moving on the down line, and the 

 wreckage also struck a light engine standing in a 

 bay clo.se by. Particulars of the loss of life have been 

 fully published, and it will be sufficient to say that 

 on the express twenty-four passengers were killed, 

 seven were seriouslv injured, the engine-driver and 

 fireman were killed, and a ticket collector and two 

 waiters on the dining car were injured. The guard 

 of the milk train and the fireman of the light engine 

 were also killed, and the driver was badly scalded. 



The chief interest of Major Pringle's report, as in 

 all reports of this nature, centres in his conclusion 

 as to the probable cause of the accident. Speaking 

 at large, there is no doubt, as we have stated, but 

 th;it the disaster was due to high speed on an awk- 

 ward curve, and the evidence all points to the fact 

 that the engine and tender turned over bodily; how 

 the forces set up acted so as to bring about the result 

 is the problem that remains to be solved. 



.\ccording to the plan of this part of the line, given 

 in the report, the up line is straight through the 

 station, but at the eastern end of the platform a 

 curve to the left of ten chains radius (compound) ex- 

 t<'n'ls for a distance of about ninetv-two yards. In the 

 body of the report is a statement attributing a radius 

 of eight chains to the curve, this representing the 

 sharpest part of it. There is a rising gradient of 

 [ in 15S, and the maximum superelevation on the 



NO. 1930, VOL. 74] 



curve is 3^ inches. It was on this part of the line 

 that the accident occurred, the overturned engine 

 being found at the termination of the curve, and just 

 in front of facing points with reverse curves of 

 7^ chains radius; naturally there could be no super- 

 elevation at the points. The report states that the 

 three leading vehicles of the express were overturned 

 in various directions, the frames stripped of woodwork 

 and completely destroyed. The fourth vehicle fared 

 little better. Comparatively little damage was done 

 to the last vehicle, which came to rest in an upright 

 position, with the last pair of wheels on the proper 

 rails. The engine and tender were both overturned 

 on their right sides, but less d.amage was done than 

 might have been expected, and the engine was shortly 

 afterwards hauled to Nine Elms on its own wheels. 

 Five vans of the milk train were completely de- 

 stroyed, and five were damaged. This destruction of 

 rolling-stock was accompanied by remarkably little 

 damage to permanent viay on the up line over which 

 the express was running, but a length of about forty 

 yards of the down line was torn out and destroyed. 



The weight of the engine was nearly 54 tons 

 (53 tons 19 cwt.), 16 tons 17 cwt. being on the lead- 

 ing bogie, ig tons 2 cwt. on the leading driving axle, 

 and 18 tons on the trailing axle. The tender weighed 

 44 tons 17 cwt., 23 tons 2 cwt. being on the leading 

 bogie, and 21 tons 15 cwt. on the traihng bogie. 

 The centre of gravitv of the engine was calculated at 

 about 5 feet above the rail-level, and that of the tender 

 at about 4' feet. 



So far we have most of the chief data generally 

 at command for calculating what would be the limit 

 of safe speed for travelling over the part of the 

 line where the accident occurred. Calculations for 

 the centre of gravitv of an engine are somewhat 

 tedious, even when al'l data are at command, arid the 

 figures given appear somewhat low for an engine of 

 the tvpe. In former days this would have been of 

 less consequence, but the' tendency to raise the boiler, 

 so that the chimnev becomes nothing more than a 

 " frill round a hole '"—as a railway engineer recently 

 .said— makes the centre of gravity a factor that needs 

 more attention, although the effect in this respect of 

 the modern high boiler is far more apparent than 

 real. 



It is unfortunate that our chief railways were de- 

 signed for lower speeds than are now required, and 

 altogether for more primitive conditions; thus it is 

 [Xissible that when Salisbury Station was built it was 

 not anticipated that a train would ever run through, 

 and the curve of 8 chains would be without danger 

 for a stopping train. 



Major Pringle savs that the engine in question, 

 with a centre of gravity 5 feet above the rails, when 

 traversing a curve of S' chains, would be in unstable 

 equilibrium at a speed of about sixty-seven to sixty- 

 eight miles per hour, even if full allowance were made 

 for the beneficial effect of 3* inches superelevation. 

 Major Pringle does not give his calculations, but, 

 as he savs, the result mav be taken as agreeing 



WV- -r- 



with modern formulje. The rule ~ , d = E. where 



W = width of gauge in feet, V=velocity in miles per 

 hour, R = radius of curve in feet, and E = elevation of 

 outer rail in inches; or if the speed V were expressed 

 in feet per second the formula would become 

 WV-'i'R, where .? is 32-2. If the formula were 

 used to calculate the superelevation for a speed of 

 sixty miles per hour, it would give superelevation of 

 25.6' inches; on the other hand, at the speed of thirty 

 miles an hour— that laid down as a maximum by the 

 railwav company's engineers— the rule would give 



