SEA-FISHERIES LABORATORY. 179 



Samples of the black sancl were put into tall, narrow 

 glass tubes and covered with salt-water, fresh water, 5 % 

 forma' ine and 70 % methylated spirit. In all cases the same 

 thing happened : the upper 5 mm. or so of sand bleached 

 rapidly to the normal, light yellow colour and then the action 

 slackened. Very slowly the discolourised layer thickened, but 

 after some six months it was little over about 5 mm. in thick- 

 ness. Some of the black substance was put into a 12 x 3 cm. 

 tube, the latter being filled to within an inch of the top. The 

 water in the sand was drained off for about ten minutes and 

 then the upper part of the tube was dried and filled with melted 

 paraffin wax, the latter being coated over the outer edge so as 

 to make an air-tight seal. After eight months the sand 

 remained perfectly black and there was no trace of bleaching. 

 A little white substance, rather like a bacterial growth, formed 

 on the surface, but this was not bleached sand : it has not yet 

 been examined. 



Another, and similar, tube was filled in the same way, 

 but was sealed with an ordinary, unlutecl cork. The sand 

 gradually dried, but it did so unequally in such a way that air 

 was able to penetrate along irregularly dried paths. These 

 paths bleached to the usual light yellow colour while the other 

 parts remained black. Gradually, however, the whole became 

 grey or yellow, but on the margins of the " paths " an ochreous 

 substance, evidently ferric oxide (Fe 2 3 ), began to appear. 

 After eight months the whole contents of this tube had not 

 completely bleached, or reddened. 



A little of the blackest sand was placed in a glass tube of 

 2 cms. bore and about 12 cms. long. Hydrogen was generated 

 from zinc and sulphuric acid, washed in strong H 2 S0 4 , bubbled 

 through a strong alkaline solution of pyrogallic acid, again 

 passed through strong H 2 S0 4 , and finally dried in a calcium 

 chloride U-tube. The tube containing the black sand was 

 gently heated and the O-free, dry gas was passed through it 



