By PROFESSOE RAMSAY, Ph.D. 
HE skipping motion of extremely small particles has been 
I for long a subject of curiosity, but has ^s yet remained 
without explanation. The following is an attempt to ascertain 
its cause. 
1st. — It is not dependent on the life of the particle. This 
would seem an absurd notion, but it was the theory first advanced 
to account for the phenomenon. And as it was first observed by 
Robert Browm w'hen examining the pollen of plants, he had some 
ground for his supposition. Buffon attributed it to this cause, 
and Spallanzani termed the dancing particles ‘‘ animaletti 
d’ultimo ordine.” It occurs, however, with particles strictly 
mineral in their constitution, such as quartz, cinnabar, finely- 
divided gold, etc. 
2nd. — Nor does it depend on the material of which the 
particles are composed, for all substances, if in a sufficiently fine 
state of division, manifest this motion. 
(a) They may be conductors, e.g., Gold, silver, platinum. 
ih) They may be non-conductors, e.g., Sulphur, gamboge, 
quartz. 
(c) They may be absolutely insoluble in water. 
{d) They may be slowly attacked by water, e.g., Quartz, 
silicates, barium sulphate. 
[e) They may be good conductors of heat, e.g., The metals 
above-mentioned. 
