M. RaspaiPs Note on Mr Brown's Observations. 107 



ceding memoir. The author might have swelled his memoir 

 with myriads of analogous facts ; but we consider it unneces- 

 sary to adduce individual facts after the general law has been 

 ascertained. 



The author might thus have varied infinitely the motions 

 which he has observed, if he had used essential oils, globules 

 that had been kept in ether, or alcohol, or camphor, all whose 

 motions vary with the shape of the fragments which are pla- 

 ced upon the water, since they are owing to the evaporation 

 of the substance itself. To all these causes we may add the 

 electricity which the friction of the file may communicate to 

 metallic particles. 



Mr Brown would no doubt have himself recognized the 

 various causes of these motions, if he had seen the criticism 

 which we have published of a Memoir, Sur les Mycodermes^ 

 (Bull des Sc. Nat, et de Geol. Tom. xii. No. 27, p. 46 ;) — our 

 Note, Sur VEncollage a la Cuve^ read to the Institute on the 

 24th December, and published in Le Globe the end of De- 

 cember 1827; — our Memoir, Sur les Tissus Organiques, 

 published in Tom. iii. of the Memoirs of the Natural History 

 Society of Paris ; and, lastly, the announce of the same Me- 

 moir, inserted in Le Globe of the 22d March 1 828, four months 

 before the publication of Mr Brown's memoir. This article 

 was reprinted verbatim in the Bulleti7i des Sc. Nat. etde Geol. 

 for May 1828, No. 54. 



In order to render these motions visible, the microscope is 

 not indispensably necessary. Whenever we place upon water 

 organic or inorganic bodies capable of being wetted, or of im- 

 bibing water, we shall observe motions more or less singular, 

 which will vary in each experiment, and which will depend 

 only on the variations in the form of their different faces. 

 Particles of iron, for example, will move differently, according 

 as they have been obtained with a file more or less fine. Po- 

 rous bodies will move very differently from compact bodies. 



Those which have no affinity for water will move when the 

 water is agitated by the causes which we have pointed out in 

 our preceding memoir. Thus wax well freed from its vola- 

 tile oil, fat, and oil, present motions too vague to be deter- 

 mined. But dry organic fragments, on account of their avi- 



