268 Mr Arnotfs Tour to the South of France 



pressure from the under-side. The revolving cylinder will thus 

 be forced round by an equal pressure of steam on all sides, to 

 effect Y*oths of a revolution; leaving about y^jjth to the accele- 

 rated force of the fly-wheel, at which period no steam is expend- 

 ed. 



Fig. 2. H, shews the flange to connect the steam-pipe W 

 leading to the mid division ; r, r, &c. brass rings fitted on the 

 ends of the cylinders, in such a manner as to make them steam- 

 tight against the division-plates ar, x, &c. ; and R the shaft of 

 the revolving cylinders. 



In cases where a fly-wheel must be dispensed with, the pis- 

 ton-plates can be so placed on the revolving cylinders as the 

 mid one would be in action, when the end ones pass the valves, 

 and the end ones in action when the mid one passes ; but in this 

 case the pressure on the revolving cylinders would not be ex- 

 actly fair. 



London, 



7. Pratt Street, Lambeth 



21(h July \fi2ii 



] 



Tour to tlie S(mth of France and the Pyrenees^ in 1825. By 

 G. A. Walker Arnott, Esq. A.M. F.L.S. & R.S.E. &c. 

 In a Letter to Professor Jameson. (Continued from p. 78.) 



V>IN the 1st of April Mr Bentham and I left Avignon behind 

 us at 4 A. M. We arrived at Lafoux at half-past 7. This is a 

 small village on the other side of the river Gard, from and op- 

 posite to the town of Remoulins. It is the La Fourche of Sir 

 James Smith ; and I had been much prejudiced against this 

 place by some remarks I remembered to have been made by that 

 author in his Tour on the Continent. I was, however, agreeably 

 disappointed. Instead of a dirty and comfortless inn, we found 

 one remarkable for its neatness and cleanness. Many changes 

 and many improvements have, however, every where taken 

 place during the last forty years. Towards 9, we sidlied fortli 

 to see the famous Pont de Gard, which is about two miles 

 higher up the river. This remarkable bridge, or rather aque- 

 duct, consisting of three series of arches, one above the other, 



