322 A SPECIMEN OF ITACOLUMITE. 



Several small specks of more hig-hly refracting' minerals are 

 also to be observed under tbe microscope, though not evident 

 in the photo, and as these are absent from the weathered 

 specimen it seems probable that their removal accounts in 

 great part for the small observed difference in composition. 



The structure of the weathered specimen is shown in Fig. 

 III. (photo taken under the same conditions as II.), and here 

 it will be at once seen that the exteriors of the quartz grains 

 have been removed, doubtless by solution, but that the inter- 

 locking between the grains, previously referred to, prevents 

 their falling apart. 



Sections taken in other planes would doubtless show a simi- 

 lar structure, and the explanation appears to be simply that 

 the grains composing the mass are held together by this in- 

 terlocking in such a manner that a limited amount of move- 

 ment relative to one another becomes possible without actual 

 separation occurring, and consequently the flexibility charac- 

 teristic of itacolumite is exhibited. 



In conclusion, I have to acknowledge with pleasure my 

 indebtedness to Mr. J. C. Stokoe, of Pigg's Peak, for the 

 trouble taken to secure a specimen of the same bed from 

 depth, and to Mr. M. Weber, of the , Geological Museum, 

 Johannesburg, for kindly preparing the two slides for examina- 

 tion. 



BACTERICIDAL ACTION OF LIGHT. — An account 

 is given in Archives d'Elcctricitc Medical c of T. Nogier's 

 recent experiments in regard to the sterilising action of the 

 light from mercury-vapour quartz lamps on water intended for 

 drinking purposes. Pathogenic microbes within a radius of 

 30 cm. from the source of light were destroyed by one minute's 

 exposure to rays of short wave-length, and 26 gallons of water, 

 in which colon and typhoid bacilli were present, ' were 

 completely sterilised by a two minutes immersion of the lamp 

 in the tank. This sterilisation M. Nogier attributes not to 

 any process of oxidation but solely to the action of the light. 

 G. Vallet, in Comptes rcndus pp. 632 — 634 declares that the 

 ultra-violet rays from the above lamps pass readily through 

 such liquids as ethyl alcohol, glycerol and certain saline 

 solutions, but are stopped if the liquid contains albumen, 

 peptone, or oils. Under the latter circumstances, therefore, 

 the colon bacillus is not destroved. 



