18 69. J Engineering — Civil and Mechanical. 433 



hydrogenium. It consisted of a coil formed with a strip of jDalla- 

 dium aud a strip of platinum, each being 300'"'"- long, 3'""'- wide, 

 and 0-3'"™- thick. This is put into a glass vessel filled with acidu- 

 lated water ; a plate or wire of platinum is placed near it, and the 

 ribbon or wire connected with either pole of a battery by means of 

 a conmiutator. The coil is first connected with the zinc pole of the 

 battery, hydrogen is then thrown on the surface of the metal, 

 which consumes the jireviously occluded hydrogen, and causes the 

 index to move rajiidly back to zero. 



6. ENGINEEKING— CIVIL AND MECHANICAL. 



(Proceedings of Societies and recent Publications.) 



In order to accommodate the increasing demand for facihties of 

 transport fostered by the continued extension of our railways, lines 

 of communication are now demanded in directions where, until 

 recently, they were never thought of, and the passage of rivers — 

 and other obstacles, which, in the early days of engineering, would 

 have been carefully avoided — is now boldly efiected as a matter of 

 course. It is perhaps difiicult to say exactly to what length of span 

 a bridge may be built, but for practical purposes it is found that 

 the largest spans are most easily obtainable with bridges con- 

 structed on the suspension principle. CoupHng this fact with the 

 recognized want of imj^roved means of communication between this 

 country and the Continent, M. Boutet has put forward a scheme 

 for erecting a bridge across the channel from the Shakspeare Clifi", 

 Dover, to Cape Blanc Nez, on the opposite coast ; it is to consist 

 of ten clear spans, each 3282 yards long (nearly two miles), with a 

 platform 360 feet above the average sea-level. Impossible as we 

 believe the realization of such a work to be, its author has, it is 

 understood, succeeded in recommending his plan to the favourable 

 notice of the Emperor of the French and Earl Granville. Projects 

 have been put forward also for crossing the channel by means of a 

 tunnel or subway, but the great question in connection with such 

 works, and which must ultimately settle the point, is. Will they 

 pay ? Supposing it to be clearly demonstrable that they would 

 prove remunerative when completed, is the yearly increasing trafiic 

 to be subject to the numerous inconveniences from which it now 

 suffers during the many years such works would be under con- 

 struction ? 



Very different, however, to the above schemes is the joint 

 proposal of Messrs. John Fowler, James Abernethy, and WiUiam 

 Wilson. According to this plan railway trains would be conveyed 



