104 BEPORT — 1842. 



any country. Details were prepared to show this, drawn from actual estimates 

 made for the purposes of determining the expense of the apparatus and railway under 

 several greatly differing circumstances ; and the various economies contemplated were 

 mentioned. It was also observed that the recent improvements and simplifications 

 by Prof. Wheatstone of his electro-magnetic telegraph, had veiy greatly reduced the 

 expense of that invaluable invention ; so that for this indispensable accompaniment 

 of the atmospheric railway, no more than £100 per mile would be required. Much 

 stress was laid on the advantage of getting rid of the locomotive engine, which is a 

 constant source of dangers and accidents, and has always been the cause of the most 

 fatal ones ; at the same time adding greatly to the unprofitable weight of the train, 

 and requiring everything connected with the present details of railway construction 

 and furnishing to be proportionably large, heavy and expensive. On the atmospheric 

 system, the rails, and upper works generally, the carriages, vehicles, stations, build- 

 ings, and establishments, &c, will be all very much less costly. In laying out a 

 line, it may be suited to the undulations of the country, and earth- work greatly re- 

 duced ; bridges, and all other works of art, will be on a much smaller scale, not 

 simply in the arithmetical proportion of their heights or breadths, but more nearly 

 in proportion to the cubes of those dimensions ; and generally a saving in land, 

 damages, &c. 



But the great paramount advantage is the perfect safety from collisions and 

 similar accidents, on the single lines of the atmospheric system, which railways 

 worked by locomotive engines, even with double lines, cannot possibly be free from. 



Reverting to the stationary power, it was stated that the adoption of other 

 means than steam to work the air-pump and produce a vacuum in the tube, might 

 often be expedient and economical ; as water, where abundant, or where it could be 

 collected in reservoirs ; or where trains were not constantly passing, a small steam- 

 engine might be continually at work raising water to be used (over and over again 

 if needful) at the stated times when the traffic had to pass, and a short experience 

 would determine the exact quantity of water required to work a wheel for these given 

 periods ; and as the time necessary to produce the required exhaustion in any length 

 of tube is probably the same that the carriage would take to travel over the 

 same space, the exact measure of power to create and sustain the vacuum could be 

 calculated. But it is clear that the importance of obtaining the very cheapest 

 method of exhausting the tube would soon attract the attention of scientific and 

 practical men. 



Allusion was made to the facilities which this system possessed of disengaging 

 the train from the piston-rod moving in the tube; and also to the very short space 

 in which the train could be stopped, by the ordinary break, and by destroying the 

 vacuum in front of the piston ; rendered still more easy by the absence of the vast 

 momentum, which from the weight of the locomotive and the heavier carriages, 

 is always an accompaniment of the present trains. 



A summary of the principles of the atmospheric railway concluded the lecture ; 

 the Professor observing that the invention was but in its infancy, and that it was 

 scarcely possible to appreciate the results, when further developments, practically 

 brought out on a large scale, should bring this wonderful power still more within 

 the grasp and command of man. 



Various models, drawings, tables, and formulae were exhibited to the meeting, 

 and constantly referred to in the course of the lecture, of which they were intended 

 to be illustrations. 



On Straight Axles for Locomotives. By Professor Vignoles. 



He stated that an unfounded prejudice existed in favour of cranked axles, which, 

 in his opinion, were inferior to straight ones in almost every point of view. With 

 straight axles the cranks were thrown outside the wheels, which gave more room for 

 the arrangement of the working parts ; and another great advantage was gained by 

 lowering the boiler nearly fifteen inches, and thereby increasing the safety of the 

 engine, by placing the centre of gravity nearer the rail. The original expense of the 

 engine and of the repairs was also much lessened. These advantages might be 

 shown by a reference to the Dublin and Kingstown Railway. By introducing 

 straight axles and outside cranks the expenses had been greatly decreased, no acci- 



