Origin of the Brownian Motions. By Rev. J. Delsaulx, S.J. 7 
visible. My studies of this question were long before the experi- 
ments of Mr. Crookes, and none of the data now available were 
known. It would require a good deal of consideration before 
saying positively that the author has completely explained the 
whole phenomenon ; but at all events I am not able to mention any 
fact which is not to be reconciled with his theory. 
Whilst thus writing on the subject, I may as well mention that 
I have very recently observed a curious fact in connection with it. 
I have found that very minute granules of kaolin, massed together 
so that the particles cannot move to and fro, do yet show that 
there is a real movement. When examined under polarized light, 
they twinkle in such a way as to prove that their axis of double 
refraction alters its position ; they rotate, although they do not 
visibly move. 
