12 NATURAL SCIENCE. Jan., 



they previously existed as reef gold. On the other hand, many 

 authors believe that particles of alluvial gold may have increased in 

 size by electroplating themselves in the drifts where they lie. 



Alluvial gold is generally supposed to be richer and more pure 

 than reef gold, and is therefore credited with a different origin. Gold 

 is soluble in solutions of alkaline sulphides, carbonates, and silicates, 

 and it is suggested that the nuggets have been derived from percola- 

 ting auriferous waters. Sea-water undoubtedly contains gold, and 

 the precious metal is being deposited at the present day from the hot 

 springs of Nevada and California. 



Professor Liversidge, as he narrates in a paper read before the 

 Royal Society of New South Wales, has himself caused gold nuggets 

 to grow by immersing them in photographers' gold toning solution, 

 together with sand, pyrites, and other minerals. Yet he concludes 

 that such has not been the origin of the large gold nuggets, for they 

 are found with other auriferous pebbles which are admittedly derived 

 from reefs ; further, he denies that there is any essential difference in 

 composition between reef and alluvial gold, and asks why the latter, 

 if formed in situ, does not occur in strings and plates. 



We may add that nuggets occasionally bear impressions of 

 crystallised minerals upon which they must have been deposited, and 

 therefore in a vein : this is the case with one of the largest nuggets 

 in the St. Petersburg Museum. 



On the whole it does not appear that gold will grow any more 

 rapidly if buried in alluvial deposits than when invested in the more 

 ordinary way. 



Sterilised Foods. 



These are the days when the bacteriologist, advertising or other, 

 cannot sleep the sleep of the just unless he has suggested a new 

 terror to the hypochondraical public. Italian ices, water-cress, 

 oysters, milk, and kissing — each dear delight or domestic necessity in 

 turn is declared a poison. We cannot reassure the timorous by 

 declaring the warnings quite unfounded. We are certain, even, that 

 as the number of those on the quest for microbes increases, the 

 number of places where microbes associated with disease are found 

 will also increase. For microbes have an astonishing vitality : they 

 themselves, or their spores, frequently are unaffected by any applica- 

 tion of heat save prolonged boiling or the higher temperature of 

 roasting, by antiseptics, save in concentrated form and after pro- 

 longed application, or by alcohol in any of its potable forms. Their 

 tenacity of life, their power of rapid multiplication, and the facility 

 with which they spread from place to place, secure their presence in 

 almost every conceivable spot. 



In this omnipresence of microbes the timorous may take refuge, 

 and pursue their wonted habits of eating and drinking and kissing 

 untroubled by the sinister suggestions of bacteriologists. They may 



