Page 53
centreing his imagination in changed to
[centring] his imagination in

Page 64
light on B would be only four twenty-fifths changed to
light on B would be only [four-twenty-fifths]

Page 65
and cut out an aperature corresponding changed to
and cut out an [aperture] corresponding

Page 66
at a proper heigth from changed to
at a proper [height] from

Page 69
Having discribed in the last changed to
Having [described] in the last

Page 70
as it sometimes called changed to
as [it is] sometimes called

Page 71
and the effect be improved.. changed to
and the effect be [improved.]

Page 83
If he find that he is not changed to
If he [finds] that he is not

Page 87
so dilute the reduction takes places very slowly changed to
so dilute the reduction takes [place] very slowly

Page 88
common desinfecting powder changed to
common [disinfecting] powder
it as as well to have two changed to
it [is as] well to have two