Mechanical Science. 369 



3. CLEMENT'S EXPERIMENT EASY MODE OP REPEATING IT. 



The very curious, and apparently paradoxical experiment, first de- 

 scribed by Clement, in which air, gas, or steam, issuing with force 

 from a hole in a flat surface, did not blow away a platter or other flat 

 and extended body, but rather caused its adhesion, has been repeated 

 since in a great variety of forms. M. Hachette contrived a simple 

 little apparatus, by which every one was put in possession of the power 

 of witnessing the effect: and such facilities are valuable, because they 

 rapidly extend the knowledge of curious effects, and cause them to be 

 still more extensively pursued and investigated. The experiment 

 may be still further simplified in the following manner. When the 

 fingers of the open hand are retained as close to each other as they 

 can be, still there are certain slit-like intervals between them extend- 

 ing from joint to joint. Let the hand be held horizontally with the 

 palm downwards, apply the lips to the interval between the second 

 and third fingers nearest to their roots, and then blowing with force, 

 a strong jet of air will of course issue from the aperture at the under 

 side of the hand. Now, put a piece of paper or a card three or four 

 inches square against that aperture, and again blow ; it will be found 

 that the paper will neither be blown away, nor fall by its own weight, 

 but will be pressed upwards against the hand and the issuing current 

 of air, so long as that current continues. The moment it ceases, the 

 paper will fall away by its own gravity, in obedience to the ordinarily 

 active laws of nature. M. F. 



4. BROWNE'S MOVING MOLECULES. 



Muncke, of Heidelberg, finds the following a simple and easy mode 

 of showing the motions of particles ; triturate a piece of gamboge 

 the size of a pin's head in a large drop of water on a glass plate ; 

 take as much of this solution as will hang on the head of a pin, 

 dilute it again with a drop of water, and then bring under the micro- 

 scope as much as amounts to half a millet-seed ; there are then 

 observable in the fluid small brownish-yellow points, generally round 

 (but also of other forms), of the size of a small grain of gunpowder, 

 distant from one another from 0.20 to 1 line. These points are in 

 perpetual motion, varying in velocity, so that they move through an 

 apparent space of 1 line in from 0.5 to 2 or 4 seconds. If fine oil 

 of almonds be employed in place of water, no motion of the particles 

 takes place, but in spirit of wine it is so rapid as scarcely to be 

 followed by the eye. This motion certainly bears some resemblance 

 to that observed in infusory animals, but the latter show more of 

 voluntary action. The idea of vitality is quite out of the question. 

 On the contrary, the motions may be viewed as of a mechanical 

 nature, caused by the unequal temperature of the strongly illuminated 

 water, its evaporation, currents of air, heated currents, &c. If the 

 diameter of a drop be 0.5 of a line, we obtain, by magnifying 500 

 times, an apparent mass of water of more than a foot and a-half 



