■ 



MOTIONS OF ODOROUS SUBSTANCES. 51 



difcufTed, is that the razor fliould be in good 1 order : and that 

 all the other particulars may be varied, except trie mechanical 

 procefs of cutting; — that the great fecret of taking off the Eflentialpartof 

 beard with facility, confifts in a drawing ftroke, that is to lay, manipulation. 

 that the line of the motion of the razor itfelf mould be very 

 oblique to the line of the edge, and not at right angles to 

 that line, as is commonly practifed ; fo that the , tool may be 

 made to exert its action as a favv, which is much more pow- 

 erful than its iimplc effect as a wedge. This method is in- 

 deed fo very effectual, as to require great care and consider- 

 able practice before it can be adopted, in the extreme, with 

 perfect fafety ; but the fame efficacy which endangers the 

 ikin, renders it eafy and pleafant with regard to the beard. 



XII. 



sib/tract of the Enquiries of CiT. Benedict-Prevost, and 

 fame other Natural Pliilofophers, relative to the Motions »■■•' 

 Odorous Subjlances placed upon Water. By Cit. BiOt *. 



IT is a fact, which has long been known to natural philofo- Motions of cam- 

 phers, that fmall pieces of camphor, when placed upon water, P nor » &c « u po» 

 have a very rapid rotatory motion. Volta and Brugnatelli " 

 have obtained the fame remits, by employing the benzoic and 

 fuccinic acids. Citizen Benedict Prevoft has extended this 

 property to a great number of odorous fubftances. 



But however unanimous philofophers have been in admit- 

 ting the fads, they differ greatly from each other" in the ex- 

 planations they have given. 



Citizen Prevoft attributes thefe motions to the emanation of Difcuflions re- 

 the odorous particles of the bodies : The experiments upon f P e & ,n 8 their 

 which he grounds this opinion may be found in the numbers 

 that have been quoted. Venturi, ProfefTdr of Natural Philo- Venturi fuppofe* 

 fophy at Modena, applies to thefe phenomena the explanation the aftion *f 

 which Monge has given of the apparent attractions of fob* 

 fiances floating upon the furface of water : according to him, 

 " the water has a ftronger attraction for the folid camphor, 



* Soc. Philom. 54. The experiments of Prevoft, Venturi, and 

 Carradori, alluded to in this notice, are given in the Philofophical 

 Journal, 4toj for which fee the Indexes. N, 



£ ? than. 



