226 The Microscope. 



gently agitating it; this will occasion the molecules to be transfer- 

 red to the water upon the glass, which is then in a state to be 

 submitted to the deep powers of the microscope: to separate the 

 molecules from the glass itself, either pound it very fine, or gently 

 rub together the unpolished edges of two pieces, having previous- 

 ly wetted them — the produce can then be transferred to a drop of 

 water. 



The figure of the molecules is spherical: they are so minute 

 that four hundred millions of them would not occupy greater space 

 than a superficial square inch. Their motion is very vivid, and 

 consists, not only of a change of place in the fluid, manifested by 

 alterations in their relative positions, but also, not unfrequently^ 

 of a change of form in the particle itself; each molecule appears 

 to revolve upon its axis: in fact, the whole of the motions are 

 very similar to those of the most minute kind of animalcules inhab- 

 iting water. 



Some persons have considered the motion to result from the 

 evaporation of the fluid and the action of the breath of the obser- 

 ver upon its surface: this is proved not to be the case, by cover- 

 ing the water with a thin piece of talc, when the motions continue 

 unaltered; it has likewise been urged that these spherical mole- 

 cules may be hollow, and that the motion is produced by the wa- 

 ter entering them, thereby displacing the air contained in them — ■ 

 were this the case, the action must soon subside, which does not 

 lake place: besides, the molecules are proved to be suspended 

 within the fluid, by bringing the surface to the true focus, when a 

 variety of irregular particles (distinct from the molecules) will be 

 discovered evidently acted upon by exterior causes. 



When it is considered that there is not the slightest difference 

 in the general figure of these active molecules (let the substance 

 be what it may, from which they are separated,) it will be conced- 

 ed that their identity gives them a character which makes it diffi- 

 cult to prove their figure and motions to be the result of mere 

 chance, exterior mechanical causes, or optical delusion; this has 

 been kindly shown by Mr. Brown to the editor, who is perfectly 

 of that gentleman's opinion. 



Infusaria, or animalcules in vegetable infusions. The 

 smallest living creatures we are acquainted with, are the animal- 

 cules in fluids; they afford a wonderful scope for inquiry, and 

 inothing is more capable of affording instruction combined with 

 amusement, than researches into the secrets of Nature in the more 

 minute parts of her works; and it presents to view the most sur- 

 prising wonders hitherto unknown; for who would or could have 

 raagined that, in a single drop of water, thousands of living crea- 



