MAGNITUDE AND MINUTENESS. 



it, a film of moisture wiH remain upon it, and the drop will not be 

 visibly diminished. Yet this film of moisture will still be sweet, 

 and will, therefore, contain a fraction of the 31000th part of the 

 lump of sugar, too minute to admit of numerical estimation. 



29. It may be asked, whether we are then to conclude, from 

 these various facts, that matter is infinitely divisible, and that 

 there are no original constituent atoms of determinate magnitude 

 and figure, at which all subdivision must cease. Such an infer- 

 ence, however, would be unwarranted, even if we had no other 

 means of deciding the question except those of direct observation, 

 as we should thus impose those limits on the operations of nature 

 which she has imposed upon our powers of observing them. 



Although we are unable, by direct observation, to perceive the 

 existence of molecules, or material atoms of determinate figure, 

 yet there are many observable phenomena which render their 

 existence in the highest degree probable, if not positively 

 certain. 



30. The most remarkable of such phenomena are observed in 

 the crystallization of salts. 



"When salt is dissolved in distilled water, as in the preceding 

 example, the mixture presents the appearance of a transparent 

 liquid like water itself, the salt altogether disappearing from sight 

 and touch. The presence of the salt in the water, however, can 

 be established by weighing the solution, which will be found to 

 exceed the original weight of the water by the exact amount of 

 the weight of the salt dissolved. 



Now, if this solution be heated to a sufficient temperature, the 

 water will gradually evaporate ; but this process of evaporation 

 not affecting the salt, the remaining water will still contain the 

 same quantity of salt in solution, and it will consequently 

 become, by degrees, a stronger and stronger saline solution, the 

 water bearing, consequently, a less and less proportion to the salt. 

 The water will at length be diminished, by evaporation, to that 

 point, that a sufficient quantity does not remain to hold in solu- 

 tion the entire quantity of salt contained in it. "When this has 

 taken place, each particle of water which is evaporated leaving 

 behind it the salt which it held in solution, and this salt not 

 being capable of being dissolved by the water which remains, it 

 will float in such water in its solid and natural state, undissolved, 

 just as particles of dust, or other matter not soluble in the water, 

 would do. But the saline particles which thus remain floating in 

 the liquid undissolved, will not collect in irregular solid pieces, 

 but will exhibit themselves in regular figures, terminated by 

 plane surfaces, always forming regular angles, these figures being 

 invariably the same for the same species of salt, but different for 

 204 



