412 WALNUT BACTERIOSIS. 



The chief object of the account just given is to record the 

 presence of the wahiut bacteriosis in several localities in South 

 Africa, and to show that it is identical with the Californian 

 walnut blight. 



Botanical Laboratories, 



Union Department of Agkuultlue, 

 Pretoria. 



Paraffin Paper Dressings in Surgery. — An 



article in TJie Journal of the American Medical Association 

 suggests the use of paraffin paper as a non-adherent dressing for 

 burns and other similar conditions. Ointments may be applied to 

 the paraffin paper before the latter is placed on the burned area. 

 Not only does such a dressing completels' exclude air, but it has 

 the advantage of being easily removable for re-dressing. 



Radioactive Colouring of Minerals. — The 



source of the varied and beautiful exotic colours which occur 

 in certain minerals has never yet been satisfactorily explained ; 

 but in view of the now well-known action of radium on glass, 

 an action which, when prolonged, colours the glass violet, and 

 imparts to it the property of emitting a violet light when heated 

 with concurrent loss of colour, Xewbery and Lupton have 

 recently investigated the effect of the ])resence of radioactive 

 substances in the colouration of a number of minerals. An 

 account of these investigations is given in Manchester Memoirs* 

 The most interesting minerals dealt with were the fluorspars, 

 all the naturally coloured specimens <_)f which were thermo- 

 luminescent, and lost their colour on heating. The fluorspars 

 showed a green glow under the action of radium and a violet 

 glow in the cathode rays. A green fluorspar, heated until all 

 the colour was discharged, re-acquired the same depth of colour 

 on exposure to 25 mgs. of radium for four days, but longer ex- 

 posure did not further increase the intensity of colour. A yellow 

 crystal similarly treated acquired a blue colour, which became 

 purple in two months without further treatment. Radium as 

 w^ell as cathode rays coloured rock-salt brown, potassium bromide 

 sea green, and potassium iodide brown : sylvine was coloured 

 an evanescent blue by radium, but deep violet by cathode rays. 

 The natural blue colour of celestine is discharged by heat, but 

 is restored by the action of radium. Details were also given of 

 experiments on diamond, sulphur, varieties of quartz, halides 

 and sulphates other than those mentioned above, phosphates, 

 silicates, and carbonates. The authors are of opinion that 

 thermo-luminescence, cathode-ray colours, and exotic colours in 

 minerals are due to dissociation of traces of impurity in the 

 bodies concerned, and not to decomposition of the body itself. 



*62 [3] Memoir Xo. to (ipiS). 



