EXPERIMENTAL AND THEOEETICAL RESEARCHES 



ON 



THE FIGURES OF EQUILIBRIUM OF A LIQUID MASS 



WITBDKAWN FROM THE ACTION OF GRAVITY, &c. 



BY J. PLATEAU, PROFESSOR AT THE UNIVERSITY OF GHENT, ETC 



From the Memoirs of the Eoyal Academy of Brussels. 



INTRODUCTIOiN BY THE SECRETARY OF THE SMITHSONIAN INSTITUTION. 



[The interesting investigations of wliicli we commence in tliis article to give 

 an account consist of* a series of parts originally published in the Transactions 

 of the Brussels Academy. A translation of the hrst three parts was published 

 in Taylor's Scientilic Memoirs ; the remainder has been translated for this 

 Institution, and the whole will be published in this and the next volume of the 

 Smithsonian Annual Reports. The author has devised an ingenious method 

 by which a. liquid may be withdrawn, as it were, from the influence of gravity, 

 and left free to assume the figure or external form which is produced by the 

 interaction of its own molecules. The experiments described in the first and 

 second parts of the series have excited much interest, and have frequently been 

 presented in popular lectures as precise illustrations of the mode of formation 

 of Saturn's ring, and almost conclusive proofs of the truth of the hypothesis 

 of La Place as to the genesis of the solar system. 



It should, however, be observed that the force in operation in the phenomena 

 of the heavenly bodies and that in the experiments of our author are very dif- 

 ferent, and can only give rise to accidental similarities, and not to identical 

 results. Gravity, which is operative in the first case, is the most feeble of all 

 known attractions, while its sphere of action is indefinitely great. On the 

 other hand, molecular attraction, v.diich is operative in the second case, is 

 exceedingly energetic, while its sphere of action only extends to the nearest 

 contiguous particles, and becomes imperceptible at sensible distances. The 

 great power exhibited by the earth on heavy bodies, near its surface, arises 

 from the combined effect of an immense number of attracting atoms. We know 

 that the attraction of the Avhole earth gives to a body near its surface a velocity 

 of 32 feet in a second, and by comparing the masses and distances from the 

 centre of the earth, and a globe of the same density and a foot in diameter, we 

 can easily calculate the velocity the latter would give a small body near its surface. 

 The velocity thus determined is less than that of an inch in a year. From 

 this result we may infer that small liquid masses, possessed of a slight degree 

 of vicidity, would never assume the form of a globule under the mere force of 

 gravitation. On the other hand, the great power of molecular attraction is 

 shown by the energy with which water is drawn into wood and other porous 

 substances. 



