1870.] Engineering — Civil and Mechanical. 403 



that steam road- rollers have been brought to sueh perfection, the 

 operation is much simplified. Road rolling has for more than a 

 quarter of a century been officially applied over the whole extent of 

 the French and Prussian roads, which are kept up under centralized 

 State superintendence, and perhaps one of the strongest arguments 

 in its favour may be given in the words of the surveyor of the roads 

 near Coblentz, in Prussia, who has observed that as " everywhere in 

 Prussia and in France the highways are rolled, if the systems were 

 not good the expense would not be incurred." Space will not admit 

 of our entering further iuto this subject now ; the whole question 

 has recently been very ably and fully discussed by Mr. F. A. Paget, 

 C.E., in a pamphlet entitled ' The Economy of Steam Road-rolling,' 

 to which we would refer our readers for further information on this 

 head. 



The recent movement in favour of tramways in London has 

 resulted in the construction, by the Metropolitan Street Tramways 

 Company, of two short lines, together about four miles in length, 

 the one at Brixton and the other between Whitechapel and Bow. 

 The tram adopted by this Company, and which may class, perhaps, 

 as the best in form hitherto introduced for the purpose, consists of an 

 iron groove fixed level with the surface of the paving, on which the 

 flange of the omnibus wheel travels. The lines are double, and be- 

 tween them as well as in the space between the trams, and strips on 

 either side of about 20 inches wide, the ground is paved with granite 

 sets. The plan of the road, which consists of longitudinal wooden 

 sleepers laid upon concrete, admits of the repair of the tramway, by 

 lifting up lengths of tram and sleeper, without breaking up the road 

 beyond the width of the tram (four inches), and a few stones here 

 and there to undo the fastenings. 



Single Bail Permanent Way. — Amongst other novelties of 

 recent introduction, and which come under the category of " Tram- 

 ways," we may mention two projects for single-line rails. The one 

 by Mr. W. J. Addis, of Tannah, near Bombay, has already been put 

 into practice in India, where it is reported to work very favourably. 

 In this case the rail is intended to be laid down either upon any 

 existing line of road, or on roads made especially for the purpose of 

 a tramway. One of the advantages claimed for this kind of line is 

 that ordinary carts may run upon it, the only necessary alteration 

 being the addition of a central wheel, or wheels, according to the 

 length of the vehicle ; the additional wheels being attached to the 

 bottom of the platform of the carts, and having a flange on either 

 side to prevent any moving off the rail. These wheels work on a 

 swivel attached to a screw, by means of which the ordinary side-wheels 

 are raised slightly off the road, so that the whole weight of the 

 vehicles rests upon the central rail. 



The second single-rail project to which we have referred was 



