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CONSTRUCTIOX OF MAPS IN RELIEF. 

 By H. G. HENDERSON. 



(Read 23rd May, 1905 J. 



Mr. H. G. Henderson, principal of the School of Mining, Truro, 

 introduced an invention of his, for which we understand a patent 

 has been secured, for map modelling or the construction of maps 

 in relief. A series of interesting relief maps, constructed on this 

 new system, was exhibited, consisting of "The Battle-field of 

 Hastings " with the Norman and Saxon armies in relative 

 positions, a similar model of the field of Bannockburn, and other 

 relief maps of parts of Wales, Cornwall, &c. Mr. Henderson 

 remarked that the best system of map-modelling hitherto in use 

 consisted in laboriously building up a superstructure of thin 

 boards, each cut by the fret-saw to the intricacies of the several 

 contour lines on the map. On this skeleton or framework the 

 map was finished off in plaster. If duplicates were required a 

 clay moidd had to be made from the original map and casts 

 taken therefrom. Under the new system no boards, tediously 

 cut to shape with the fret-saw, are required, but ordinary 

 potter's clay is simply rolled out into slabs and the mould is built 

 therefrom direct. A shallow wooden or zinc tray with a bottom 

 of wire-netting is then superimposed on the mould and liquid 

 plaster is poured in. After an hour or two, to allow the plaster 

 to set, the cast is removed from the mould and coloured and 

 finished in the usual manner. The clay mould is then immersed 

 in an oil bath, where it will keep unchanged for months or 

 years, allowing casts to be taken from the same whenever 

 required and in unlimited numbers. 



A novel feature is the filling up of the hollows of the mould 

 with coal ashes or cinders before the plaster is poured in, by 

 which means great economy of plaster and of weight is obtained, 

 while the finished cast differs no whit in appearance from solid 

 plaster and is as strong, if not stronger. In the old system 

 relief-maps of large size had to be cast in sections — always 

 detrimental to the "tout ensemble," but under the new method 

 casts in one piece can be obtained of jjractically any size. The 



