FRENCH EXHIBITION. 





jner Clark, in 



the establishment of a pneu- 

 matic tube, of small diameter, which would 

 el or carrier, any num- 

 f di-patchcs, \\hieh couNI be drawn in 

 "!i b> a vacuum and propelled in 

 t direction by air-pi ^uch a 



-.', as fixed between the Electric Cotupa- 

 ntral station, J.othbury, and the Stock 

 1 1 lire, in is;,:;. The system was subse- 

 quently extended to Cornhill, Mincinir Lane, 

 Mr. Clark adopteil lead tubes 1J inches 

 in diameter, protected by externally split 

 wn>u_rht-iron pipes. Mes>rs. Million and Rou- 

 art, the adapters of this system in Paris, use 

 \vrouirht-iron pipes, of nearly the same diaim- 

 it. length, <rla/.cd in the interior, and 

 connected by union joints rendered air-tight 

 ioutehouc. The carriers are either of 

 metal or leather the London of gutta-percha; 

 they are made short, so as to take the sharp 

 curves which are necessary in going round 

 the corners of streets. Messrs. Mignon and 

 Kouart have applied the system to the small 

 branch stations by making use of a barom- 

 eter of water to produce a vacuum, and 

 the pressure of the water-pipes of the city 

 to produce compression. The latter is, how- 

 only in practical use at present. Its 

 principle is this: At each station there is a 

 cylinder, whoso volume is double that of the 

 pneumatic tube, communicating to the next 

 station. Communication between the cylinder 

 and the tube is closed. The water is admitted 

 into the cylinder until it is half filled. It is 

 clear that the air is compressed into one-half 

 its volume, and thus pressure is produced suffi- 

 cient to drive the carrier with great speed to 

 the other end of the tube. It is calculated 

 that each carrier will carry 40 messages, and 

 that 12 carriers can be sent together, bearing 

 480 dispatches, and that 12 trains can be sent 

 per hour, and that the running of each train 

 costs about 28 centimes. 



Artificial Stone and Terra-cotta. Stones 

 made from sand and hydraulic lime have 

 been in use for a very considerable length of 

 time, and they have been found particularly 

 suitable for structures exposed to the action of 

 the sea, in which positions they are decidedly 

 superior to any natural stone that can be con- 

 veniently substituted in such localities. The 

 Exhibition contains a very rich collection of 

 stones of this kind, many specimens having 

 been taken up after having been exposed to the 

 action of the waves for a succession of years 

 without deterioration. Stones of this kind are 

 of a very rough appearance, and suitable only 

 where large and massive blocks are required, and 

 beauty or regularity of surface no object. For the 

 purposes of ornamental building, hydraulic lime 

 etimes mixed with fine-grained sand, and 

 ves a material of every suitable quality ; 

 examples of which are given in several depart- 

 iii' -nts, applied to objects of fine art and to 

 architectural decorations. Such stone moulds 



u ly well, and does not shrink in netting, 

 but its color i- very unpleasant, bc-hitf a dull 

 dark gray. The hardiu-s and durability . 

 material depend to a great extent upo: 

 proportion of cement, which it contains. Some 

 inventors have made artificial stone from sand 

 cemented together by asphalte or coal-tar. A 

 V.T\ larL'e fountain lia-in of .such a material 

 is shown in the park by M. Bourgeois, of Paris. 

 A similar material is also used in Paris for the 

 pavement of the streets \\ith success. The 

 streets are prepared in the same manner as for 

 the common macadamized roads, and are then 

 covered with a layer of sand and mortar, after 

 which the mixture of sand and asphalte is spread 

 and pressed down with a heavy roller. The 

 roads are extremely smooth and even, without, 

 at the same time, being slippery in wet weather ; 

 they raise very little dust when dry, and make 

 no mud when covered with water. The car- 

 riage-wheels move over them absolutely noise- 

 lessly, there being nothing heard bnt the 

 muffled sound of the horses' hoofs. Of the 

 artificial stone exhibited the most important 

 and valuable is the concrete stone of Mr. Ran- 

 eome exhibited in the British department. This 

 stone consists of sand and cement of silicate of 

 lime, produced by a purely chemical process, 

 between the particles of sand when in the 

 mould. It combines the advantages of facility 

 of moulding, and absence of contraction in set- 

 ting, with those of great hardness and strength, 

 and with a fine color, variable at will from the 

 purest white through all shades and tints. 

 The most important exhibition in the French 

 department is that of the works at Lafarge-du- 

 Teil. This establishment has been in existence 

 85 years ; it consists of a quarry for hydraulic 

 limestone, situated at the banks of the river 

 Rhone, and has gradually increased to its pres- 

 ent rate of production, amounting to 90 million 

 tons of hydraulic lime per annum. There are 

 500 workmen employed on the spot, and thirty- 

 five kilns for burning the lime are in continuous 

 operation. The principal application of the 

 hydraulic lime produced at Lafarge-du-Teil is 

 the manufacture of concrete blocks for masonry 

 exposed to the action of the sea, such as break- 

 waters, sea-fortifications, etc. Stones of this 

 kind have been applied in a great number of 

 harbor works, particularly in the Mediterra- 

 nean ; and specimens of such stones are ex- 

 hibited with the testimonials of the authorities 

 attached to them, stating how long they have 

 been exposed to the action of the sea. The 

 proportions of materials used for making this 

 concrete stone are given as follows : from 350 

 kil. to 400 kil. of lime ground into dust and 

 one cubic metre of sand are mixed together. 

 and form a mortar for blocks exposed to 

 the sea. About 300 kil. of lime per cubic 

 metre of sand give a mortar for foundations 

 in fresh water; and 250 kil. of lime and one 

 cubic metre of sand make a cement or mortar 

 for structures and >tones used in the open air. 

 For the production of artificial stones these 



