Fi:i:\ni K.\iiimn<>\. 



811 



'// sand. Thti cylinders are Of -he.-t-iron, 

 li thick, 1 foot high, ami I I'm.! i:i diam- 



Allnllt -' illcllCS tVolll till- llottolll tlleV 



aivpicm -I with holes about } inch in tlinn 

 \vliich tre >!"p!"''l w ith common corks. TM 

 In- centring tin- corks :uv removed, tlio 

 sand tlicn iiroiiu'h the holes, until 11 



emu 1 of s:ind is t'ornicd at. the base of the cylin- 

 der. The formation of this C.IH' arrest.- tin- 

 I'urt 1 1' of the sand, and therefore the 



;t nf tin- piston, until the cone is swept 

 away, \vln-n it re-forms. The sweeping is re- 

 ! until the piston has descended sufficiently 

 to detach the centring from the masonry. By 

 taking care to sweep away the same cones 

 simultaneously, the lowering of the centring 

 can he performed with perfect evenness, and as 

 gradually as may be desired by -nrnTTnuT f an 

 inch, it' neces-ary ; whilst, as no force whatever 

 lined to be used, the arch is not subjected 

 to the slightest shock during the operation. 

 This system was originated by M. Bcaudemoulin, 

 engineer in chief. 



Three fine examples of engineering are ex- 

 hihited in models, y 3 th full size, of the three 

 iron railway viaducts of Busseau d'Ahun, la 

 Cere, and du Midi ; all three of the same type. 

 Kach is composed of a lattice girder in six spans, 

 supported upon iron columns, surmounted upon 

 masonry bases. Each of the five piers consists 

 of eight hollow cast-iron columns, in two rows 

 !' four (transversely to the roadway), cross- 

 braced horizontally and diagonally with rolled 

 iron joists; these piers support four main 

 lattice girders, connected by cross-girders, 

 hearing a timber floor and continuous sleep- 

 ers. The eight columns of each pier batter 

 toward a point 148 feet above the roadway, 

 thus forming a four-sided truncated pyra- 

 mid ; the same batter is given to the masonry 

 bases upon which they are mounted ; this ar- 

 rangement gives a very pleasing effect to the 

 structure. The bases are rectangular blocks 

 of ashlar, with dressed quoins carried up from 

 the rock; the iron superstructure is secured to 

 them by eight holding-down bolts of 3 inches 

 diameter round iron. The main girders were 

 riveted together on the bank, and launched 

 into place without the use of scaffolding. 



The tunnel of Ivry, a model of which (^th 

 full size) is exhibited, is chiefly remarkable for 

 the skilful manner in which the difficulty of 

 obtaining a secure foundation for the masonry 

 of the tunnel has been overcome. 



An extremely ingenious system of siphons 

 recently applied in France to largo reservoirs 

 for the purpose of getting rid of the surplus 

 and storm waters is shown by two models. 

 The apparatus consists of two cast-iron siphon- 

 pipes, 27 inches internal diameter, T !) ( , inch 

 thickness of metal, through which the surplus 

 waters are discharged. To these are attached 

 two lesser auxiliary pipes, whose internal diam- 

 ia about 4 inches. As long as the reservoir 

 is at below its prdfecribcd water-level the siphon 

 is inactive ; bnt as soon as it rises above that 



I'-v.-l it begins to flow away through the small 

 pipe, and. the water continuing \>, 

 he-id of til- latter becomes completely sub- 

 merged ; the down-flow of the water throogb the 



small pipe draws with it the air conta'r 

 the elbow of the siphon, and the latter i 

 to work until, the discharge having n 

 the water to the prescribed level, air is read- 

 mitted ti. the bi-nd of th.- siphon and its opera- 

 tion stopped. So long as the depth of water over 

 the head of the feeder is h-^ than _' inches, the 

 whirlpool formed by the pressure of the atmos- 

 phere at the orifice causes the siphon to draw air 

 as well as water, and therefore to discharge with 

 reduced volume ; as soon, however, as the water 

 has risen to two inches above the head the 

 siphon works full bore, and discharges at the 

 rate of 1,500 gallons per second. 



The principal public buildings and restora- 

 tions executed in Paris during the last twelve 

 years are recorded in an atlas of plans exhibited 

 by the department des Travaux Publics. The 

 extent of these works may be gathered from 

 their cost, 0,630,180. The designing of these 

 works shows not only great skill expended 

 upon the construction itself, but a skilful 

 adaptation of site and judicious utilization of 

 ugly waste spaces have also contributed to the 

 general embellishment of the capital. It will 

 be remarked that in the designing of hospitals 

 and lunatic asylums great care has been taken 

 to obtain a cheerful look-out from the ward 

 windows. In the arrangement of the public 

 abattoirs the approaches from the railway sta- 

 tions have been studied so as to give the least 

 amount of street through which cattle are 

 driven, whilst the disposal of the dead meat is 

 made as easy as possible. None of these de- 

 tails have been left to take their chance. 



The most interesting object of civil engineer- 

 ing at present in progress in the world is an 

 undertaking being carried on not upon French 

 territory, but the credit of which is due to France 

 the cutting the maritime canal through the 

 Isthmus of Suez; models, plans, photographs, 

 and a panorama of which are exhibited in a 

 detached building in the park, constructed in 

 the style of an Egyptian temple. The works 

 which they illustrate deserve attention alike 

 from their great magnitude and importance 

 from an engineering point of view, and from 

 the greatness of the beneficial influences which 

 their completion is likely to exercise upon the 

 commerce of the world. The works are illus- 

 trated by a model of the isthmus on a scale of 

 yitflffjfth ; the heights are comparatively ex- 

 aggerated, GO to 1 ; the width of the canal 6 

 to 1. 



The Isthmus of Suez, at the part selected 

 for the operations of M. Lesseps, is about seven- 

 ty-two miles wide, measured as a crow flies, 

 from Pelousa, on the' Mediterranean, to Suez, 

 on the Red Sea. The levels of the-e two seas 

 is not far from identical, the mean level of the 

 Red Sea being but 6 inches higher than that 

 of the Mediterranean. Starting from Pelousa, 



