142 Progress of Invention. 



lie even between our eye and the cluster ; but its light may 

 prove insufficient to admit of spectrum analysis. Its synonyms 

 are 39 $ IV; 464 H (1833) ; 1565 General Catalogue. 



OCCULTATIONS. 



March 3rd. B 3 Tauri, 5 mag., lOh. 16m. to llh. 2m— 8th. 

 A 2 Cancri, 6 mag., 7h. 16m. to 8h. 36m. 



PEOGEESS OF INVENTION. 



Eailwat over Mont Cenis. — Notwithstanding all the aids 

 afforded by modern science, the tunnel under Mont Cenis cannot be 

 finished for several years. It has therefore been decided, in the 

 meantime, to carry a line over the Alps, following, almost 

 throughout, the route afforded by the pass of Mont Cenis. France 

 and Italy will thus enjoy the benefits of railway communication 

 within a very short period of time. To effect this, however, it will 

 be necessary to overcome engineering difficulties, which, not long 

 since, would have been deemed insurmountable. The line naturally 

 divides itself into two portions — that on the French, and that on 

 the Italian side ; and it is not the least interesting feature of the 

 undertaking that the engineers of these two nations have resolved 

 on attaining the very same object by totally different means. On the 

 French side, locomotives will be used, on the Italian, traction by ropes. 

 On the French side steam, on the Italian, water power. With such 

 gradients as must necessarily be found on this line, a sufficient 

 adhesion between the driving-wheels and rails could not possibly be 

 attained by ordinary means : a very ingenious method of producing 

 any required amount of friction has, therefore, been adopted. A 

 species of rail is to be placed between the ordinary rails : against 

 the upper and lower sides of this, rollers, driven by the engines 

 of the locomotive will act. The central rail being caught between 

 these rollers, any amount of compressing force can be obtained, so 

 as to render it impossible for the engines to work without progressive 

 motion being produced, and equally impossible for the train to 

 descend the inclined plane of its own accord, or too rapidly when 

 descent is intended. On the Italian side, the system of traction is 

 altogether different from that ordinarily used when ropes are em- 

 ployed, and it avoids some of the most serious objections to the use 

 of ropes. A strong cable is placed in the middle of the line, and 

 also an endless wire rope, which is very light, and is kept constantly 

 in motion by power obtained from falling water. "Within a waggon, 

 constructed for the purpose, is placed a drum which forms the last 

 element of a system of wheels and pinions. One turn of the cable 

 is passed round this drum. The first element of the system of 

 wheels and pinions is capable of being brought into connection with 



