332 



FKENCH EXHIBITION. 



ing electrical contact, and rendering magnetic a 

 piece of iron which withdraws a detent and 

 stops the machine. The machine is also 

 stopped should a hole occur in the web. A 

 small wheel revolves inside, and another out- 

 side the web, immediately beneath the knitting 

 plane ; conduction from one of these wheels to 

 the other is prevented by the intervening web, 

 unless a hole should occur, when contact imme- 

 diately takes place between these wheels, and " 

 the machine is stopped. A similar result en- 

 sues if a stitch should be dropped, as in such 

 event the needle, by falling below the knitting 

 plane, will, in its rotation, come into contact 

 with a brass plate placed close below the 

 needle-frame, and both needle and plate form- 

 ing a part of an electrical circuit, a bell will be 

 rung when contact takes place. 



HeliograpJiy . The display of photographs 

 in the- Exhibition is very large, and some of 

 the specimens are admirable ; there are also a 

 good many examples of photographic engrav- 

 ing on steel and copper, and of photographic 

 lithography. The photographs of Flamant, 

 Paris, are especially soft and beautiful, appar- 

 ently taken by the carbon process. There are 

 also many excellent English photographs. In 

 the French department are some sun-engraved 

 dies for stamping money or medals, executed 

 by a process invented by Mosson, a workman 

 of Lyons, and some specimens from Durand, 

 Paris, of what he calls heliogravure, which are 

 good imitations, in steel and copper, of plates 

 in old books produced in dhTerent sizes. Some 

 specimens of photo-lithography, from E. Ber- 

 thier, Paris, are very fine, but the best are Poun- 

 cy's, from Dorchester, England. Of engraved 

 plates, the best examples are those of H. Gar- 

 ner, Paris. He exhibits some excellent pho- 

 tographs, and, side by side with them, shows 

 prints taken from engraved plates, executed by 

 his process, by the sun itself, and it is difficult 

 to know one from the other. On the whole, 

 this art has made less progress than might have 

 been expected. The cylinders of the North- 

 umberland, photographed by Nelson and Oher- 

 ril, by Swan's patent carbon process, are an 

 excellent example of photographic art. The 

 specimens, too, of photo-zincography, as prac- 

 tised at the Ordnance Survey Office, in South- 

 ampton, are fair. 



Iron and Steel. The locality which this 

 class is intended to occupy, according to the 

 general plan of the Exhibition, is the great 

 circle just within the machinery gallery. The 

 nature of the objects, however, and their great 

 number necessitated many deviations from this 

 general rule. Some of the greatest iron- works 

 in France have special buildings for their arti- 

 cles in the park, others have placed their prod- 

 ucts alongside machinery in the machinery 

 gallery itself; and others, again, have availed 

 themselves of odd corners and spaces difficult 

 to find unless specially sought out. There is 

 another quantity of articles belonging to iron 

 and steel manufacture, in the sense in which 



we are accustomed to use that term, which are 

 placed in the groups of war materials and am- 

 munition which occupy places in the park. 

 There is a remarkable casting exhibited by M. 

 de Lavalle in the machinery gallery, among 

 the machinery and apparatus for mining pur- 

 poses. This is a piece of cast-iron tubing for 

 r, coal-pit or other shaft; it is 13 ft. li in. in- 

 ternal diameter, 5 ft. long, and 1 in. thick in 

 the metal, with three or four circular ribs 

 placed internally, and having about the same 

 thickness of metal as the cylindrical body. The 

 surfaces of the casting are very good, and the 

 small thickness of the body is uniform through- 

 out the circumference. Another set of most 

 extraordinary castings is shown by Messrs. 

 Dietrich and Co., of Niederbronn, in Alsace a 

 set of rings of about 5 ft. diameter, no more 

 than -jL in. thick in metal, and about f in. in 

 width. They are cast in one as a ring of the 

 intended diameter, and are about | in. thick in 

 the rough ; they are afterward turned in a 

 lathe on the outer and inner surface, an opera- 

 tion which requires extraordinary care and 

 attention. These rings, of course, have no 

 practical value, but are only exhibition articles, 

 showing the extraordinary quality of the mate- 

 rials and the great skill of workmanship. 

 Messrs. Dietrich are also the inventors of a 

 peculiar method of covering iron with an 

 *' email " which is insoluble in water and 

 diluted acids, and prevents all oxidation of the 

 surface. This " email " is spread over the inte- 

 rior surface of cast-iron vessels in a liquid 

 state, and covers internal channels, corners, 

 and grooves of irregular shape with perfect 

 uniformity. Messrs. Dietrich and Co. are also 

 manufacturers of wrought-iron articles and Bes- 

 semer steel. Among these articles exhibited is 

 a very fine wrought-iron locomotive-wheel, 

 forged with crank and counterweight, and 22 

 spokes in one piece. The wheel is 9 ft. 2J in. 

 outer diameter, and the tire, which is rolled 

 of Bessemer steel without a weld, is placed at 

 its side. The Societe Anonyme de la Provi- 

 dence exhibit a great number of disk- wheels, 

 each forged without a weld out of a solid 

 bloom ; some with their tire in one, others 

 ready for tires being shrunk over them. The 

 names of the different railways using each class 

 of these wheels are painted on the corresponding 

 specimens, and the forms and sections. are of a 

 very varied character. A very large boiler 

 plate forms the background of the Bowling 

 Iron Company ; their stand and the other arti- 

 cles are grouped in front of it. Among these 

 is a piece of an exploded boiler in a state of 

 corrugation and distortion, giving full evidence 

 of the extreme toughness and malleability of its 

 material ; a weldless tire, apparently about 8 

 ft. diameter, marked " crucible steel," and an- 

 other still larger tire made without welding 

 from one bloom of iron. There are also some 

 XI rings rolled and welded up into hoops for 

 strengthening boiler-flues. Messrs. Taylor 

 Brothers, of Leeds, have a very fine collec- 



