260 Dr. T. Stacey Wilson— The Making of Geological Models. 



temperatui'e of the surface-rocks, and not in a heated condition at 

 all ; but if it is water that has soaked in originally from the surface, 

 and has got into the neighbourhood of deep displacements of the 

 rock-crust, then we have a source of energy that is capable of being 

 dissipated to draw upon for our supply of heat, and hydrostatic 

 pressure to bring it back to the surface. We have not been forgetful 

 of the presence of radium in the waters and deposits from hot springs, 

 but as yet there are no results to communicate from South Africa. 



IV. — Notes from the Geological Laboratory of Birmingham 

 University. On a Convenient and Simple Method of making 

 Geological Models. 



By T. Stacey Wilson, M.D., B.Sc, F.G.S. 



MANY ingenious methods and materials have been used for the 

 making of geological models, to show the internal structure 

 and outci-op of a stratified sequence, to furnish maps and lines of 

 section, and to indicate the direction and effects of faults. 



Such materials and methods as those of Mr. Sopwith, while most 

 instructive and interesting, are powerless to deal with problems 

 of curved strata, and no material has yet been found by which 

 satisfactory stratigraphical models can be made of folded districts. 

 Such a material must have several properties : — 



1. It must be easily made into large plastic sheets of even 

 thickness and of distinguishable colour. 



2. It must bend readily and adapt itself sweetly to any surface 

 to which it may be applied. 



3. Successive layers must adhere together fairly quickly and 

 quite firmly. 



4. The material should set into a rigid but not brittle mass iu 

 the end, and yet not be too hard, so that it can be carved readily, 

 or if necessary moulded into any required shape. 



5. It would be an advantage if it was cheap. 



Casting about for such a substance I have found one which 

 satisfies a good many of these requirements. Not only does it 

 allow of the building up of models out of definite stratigraphical 

 elements in exact imitation of the natural geological structure, but 

 it may possibly be of use in solving certain obscure structural 

 problems. It is also likely to be of considerable use to teachers 

 and students, as models can be built up by or before a class, and 

 it may even have some applications outside geology itself. 



The material used is felt of various colours, steeped in melted 

 •paraffin wax that has a melting-point of about 110° F. 



The solid paraffin is melted slowly over a spirit-lamp or, better, 

 in a jacketed saucepan or water-bath. Layers of felt are soaked in 

 the melted paraffin and then squeezed fairly dry. The low melting- 

 point allows of this being done by hand. Layers of coloured cloth 

 may be used for thinner beds. 



The layers are then superposed one on another to tlie desired 

 thickness. They adhere together, and the composite mass may be 

 cut with a knife to any shape required. The best tools for further 



