190 Correspondence — Pivf. F. W. Sutton — Mr. Cameron. 



FAULTS. 



Sir, — If Professor Blake will kindly look at the GtEologioal 

 Magazine, Vol. III., p. 148 and Plate IX. Fig. 9 (1866), he will see 

 a notice of some faults in Malta that do not penetrate the limestone 

 lying below the bed in which they occur. These faults are thus 

 accounted for — " I suppose that the rock, being already jointed, was 

 pressed down before it was quite hard by the weight of the super- 

 incumbent strata, and the pressure on each fragment being propor- 

 tional to the area of the upper surface, those fragments which had 

 the largest upper surface in proportion to their bulk were more 

 compressed than the others, thus forming faults. The broken state 

 of many of the fossils, particularly the Echini, in this bed is a proof 

 that it has undergone considerable compression. I may, perhaps, 

 here mention that I consider that all cases of ' reversed faults ' 

 will be found to have been caused by lateral pressure." As this 

 was written nearly twenty years ago, I hope you will not mind 

 reproducing it. F. W. Hutton. 



Christchtjrch, N.Z. 



FULLER'S EARTH. 



Sir, — I shall feel obliged if you will give notice to the accom- 

 panying facts connected with the detergent properties of the fuller's 

 earth, — I mean with regard to its use as an agent in clarifying water, 

 a reference to which appeared in the Geol. Mag. for February last. 

 These strike me as being the more curious, because, as far as I can 

 learn, they are but little known. 



In the fen districts of Cambridgeshire and Lincoln, where the 

 people are entirely dependent upon the discoloured drainage off the 

 peat for their water supply, fuller's earth, brought round by dealers, 

 is used to purify the water, rendering it colourless and pleasant to 

 the taste. The method adopted is somewhat after the old fashion 

 in country districts, of placing perforated trays or letches, as they 

 were called, containing wood or other ashes, over vessels put to 

 catch the rain.^ 



To test the efficacy of fuller's earth as a filtering medium, I have 

 experimented with it upon the mineral water of Flitwick, which 

 is the colour of dark sherry and so powerfully impregnated with 

 iron''' as to act upon the palate as alum, with the result that it was 

 made nearly colourless and its strength reduced by one- half. 



Muddy water too, if filtered through it, becomes clear and free of 

 sediment. Springs issuing from beneath the fuller's earth are re- 



^ Dr. Thos. Stevenson, Guy's Hospital, has kindly written to say — • • • "fuller's 

 earth is an agent which I conceive would he very useful for the purpose, it is a 

 suhstance which would clarify, remove organic matter in solution, and also soften 

 hy carrying down chalk. 



^ Professor W. White's analysis gives 141'00 grains per gallon, oxide and car- 

 bonate of iron, "a most extraordinary amount and far exceeding the most noted 

 ch;dybeate springs in the world." E. \V. Lewis, upon "The Geology of Leighton 

 and Neighbourhood." 



