1894.] ^iO [Bache. 



from cochineal, had been observed upon by me for weeks, with a 

 one-tenth water-immersion lens, and afterwards, upon the arrival of 

 the one-fifteenth dry-lens, was observed upon without showing any 

 variation in the range and vividness of movement of the particles 

 subjected to examination. I have even covered the whole micro- 

 scope with a pall of thick, black, woolen cloth, so that not a ray 

 of light could enter it, either through the cover-glass or the eye- 

 piece, and then carefully placing the eye close to the eye-piece, 

 have suddenly thrown light upon the cover-glass, when the brovvnian 

 movement among the particles was perceived in as active play as 

 ever. I have therefore concluded, from all these experiments, that 

 neither heat nor light, nor electricity, nor magnetism, nor mechan- 

 ical shock, nor finally evaporation, is operative in producing the 

 movements; in a word, that the particles move uninfluenced by 

 these forces. I am therefore constrained to believe, upon the basis 

 of the information that I have obtained in the manner described, 

 that it is not the particles which are moved by their own energy, 

 or moved by any energy directly imparted to them from outside 

 sources, but that it is the fluid that moves them. 



If their own energy moves the particles, we should see them at 

 the same time obedient also to the law of gravitation among them- 

 selves, manifested as the resultant of whatever forces are in play, 

 whereas, although they must be obedient to the law of gravitation 

 among themselves, its effects, and generally, as well, those of terres- 

 trial gravity, are so masked as not to be at all perceptible. Now, 

 when we consider how minute all of these particles are, and yet 

 that they move apparently unhindered with such constancy and 

 force, it ought to be apparent, I should think, that they have no 

 self-motive power. However erratic the paths of individual parti- 

 cles may be, the likeness among the movements is extraordinary, so 

 almost identical in every case, varying in greatness of range and 

 rapidity only in inverse ratio to the size of the particle, that we can- 

 not conceive of self actuated particles so behaving; for relative 

 greatness of size in self-actuated particles ought to coincide with 

 relatively greater, not relatively less, energy of movement; whereas, 

 here the case is reversed. But there are other facts that I have ob- 

 served through experiment, which also prove what I say. In 

 alcohol, and as far as my experiments go, in fixed and volatile oils, 

 the brovvnian movements are not observable, and yet the micro- 

 scope plainly reveals that the movements of foreign bodies in all 



