188 THE ROYAL SOCIETY OF CANADA 



a large number of tul)er('les, at the centre of which the iron was nearly 

 eaten away. It appears quite likely, from what has l)een said by some 

 investigators, that these tulxn-cles are cultures of iron dissolving 

 bacteiia or alga?. It is quite possible that they thrive better at a 

 medium temperature and conse([uently the iron was attacked much 

 more vigorously at 50° C. than at 00° ('. Very interesting figures 

 were obtained for water which had been treated by magnesia as pre- 

 viously noted. Not only at ordinary temperatures is corrosion less 

 than for any other water examined, but the effect of the increasing 

 temperature is to still further reduce this until it is one third of that of 

 the raw or otherwise treated watei'. An explanation is here offered 

 in that the electrical potential of magnesium is veiy low and hence 

 the tendency is to keep iron out of solution. The use of light powdered 

 magnesia (MgO) is therefore suggested as a possibly suitable pigment 

 in anti-corrosive paint. 



A study of the wires under the microscope revealed scars at cer- 

 tain points, as if pieces had been bitten out. Again, highly significant 

 markings were seen on wires which had been wound together. In 

 nearly all cases "two marks were seen on either side of another of slightly 

 different appearance, indicating location and direction of "local 

 currents." Varying shades of tarnish were also noted. 



