A. Vaughan Jennings — Geology of Bad Nauheim. 359 



masses below. As the water trickles over the twigs the lime and 

 remaining iron oxides are deposited as a stalagmitic crust upon the 

 wood ; but the more soluble salts remain, and the water which drips 

 into the underlying tank is a more or less concentrated brine. 



Such is the principle of the process, but it takes one a little time 

 on the spot to discover how the mechanical difficulties are overcome. 

 The method seems to be this. The saline waters from the two great 

 ,' sprudels ' are directed into an open trench, which, empties them 

 into a large round tank situated in the fields south of the town. 

 To raise this water to the top of the ' gradirwerke ' would appear 

 a difficult task ; and yet, in spite of the flat country, the very small 

 quantity of water in the Usa, and the almost imperceptible current, 

 it is performed by means of two water-wheels. The three western 

 ' works ' are supplied by a large double pump by the Ludwig's 

 Quelle. There is not sufficient force of water to turn the wheel 

 directly, but having been once started it is able to pump up sufficient 

 water to resupply itself as well as to pass on the remainder up two 

 great pipes to the top of the framework. The eastern ' works ' are 

 similarly supplied, but in this case the wheel is as far away as 

 the village of Schwalheim beyond the railway on the east. The 

 ' connecting - rod,' if such it can be called, between the wheel 

 and the nearest of the Gradirwerke is a long series of hollowed 

 tree trunks placed end to end. These are supported at intervals on 

 the axles of pairs of iron wheels, which run on rails laid on the 

 top of low stone walls. The whole row moves backward and 

 forward some eighteen inches with the turning of the wheel. 

 A mechanical system distinctly cumbrous, but as there is no baste 

 necessary in the process it is probably as effective as any other and 

 more economical. 



The first of the solid contents of the spring water to separate are 

 the iron oxides, with which the basin of the Great Sprudel is coated. 

 In the trench leading off the waters to the Gradirwerke there is 

 a similar deposit of a powdery red oxide on twigs, leaves, etc., that 

 have fallen in. With the exception of a few diatoms and filaments 

 of cyanophyceous alg£e there seems little life here. I had expected 

 to find Leptothrix ochracea, but was unsuccessful. Further on, 

 when the lime begins to precipitate, a red porous 'travertine' is 

 produced. Almost all the remaining iron seems removed after 

 passing the tank, as the stalagmite on the brushwood is very 

 rarely tinged with red. 



At the present time there is little evident incrustation of the 

 brushwood, owing to its having been comparatively recently 

 renewed,! but the lately removed material often shows a crust 

 nearly two inches in thickness, and blocks of it are used all over 

 the neighbourhood as ornamental rockwork for gardens. 



In the western salines the brine, freed from lime and iron, 



undergoes some evaporation, and at times very delicate, hollow, 



-salt stalactites are formed, as well as imperfect or hollow salt 



crystals like the 'hopper-shaped' crystals, seen by evaporation 



> I understand that the period of renewal is about every ten years. 



