676 PLATEAU ON THE PHiENOMENA OF A FREE LIQUID MASS 



cable to all liquids ; but our experiments leave this point uncer- 

 tain. 



11. For the same diameter, and when the divisions are always 

 of their normal length, the absolute value of the time in question 

 varies with the nature of tlie liquid. 



12. In the case of mercury, and with a diameter of a centi- 

 metre, this absolute value is considerably more than two seconds. 



13. When a cylinder is formed between two solid bases suffi- 

 ciently approximated for the proportion of the normal length of 

 the cylinder to the diameter to be comprised between once and 

 once and a half the limit of stability, the transformation gives 

 only a single constriction and a single dilatation ; we then ob- 

 tain for the final result, only two portions of a sphere which are 

 unequal in volume and curvature, respectively adherent to solid 

 bases, besides interposed spherules. 



Application of the properties of liquid cylinders : theory of the 

 constitution of liquid veins emitted from circular apertures, 



69. Let us now pass to the application which we have an- 

 nounced of most of the above facts and laws. 



Let us consider a liquid vein flowing freely by the action of 

 gravity from a circular orifice perforating the thin wall of the 

 horizontal bottom of a vessel. The molecules of the liquid 

 within the vessel, which flow from all sides towards the orifice, 

 as we know, still retain, immediately after their exit, directions 

 which are oblique to the plane of this orifice ; whence there is 

 produced a rapid constriction of the vein, commencing at the 

 orifice and extending as far as a horizontal section, which has 

 been improperly denominated the contracted section. When 

 the molecules have arrived at this section, which is very near 

 the orifice, they all tend to assume a common vertical direction, 

 with a velocity corresponding to the height of the liquid in the 

 vessel ; and they are, moreover, urged in this direction by their 

 individual gravity. Hence, supposing the orifice to be circular, 

 the vein commencing at the contracted section tends to form an 

 almost perfect cylinder, of any length ; but this form is modified, 

 as we now know, by the acceleration M'hich gravity imparts to 

 the velocity of die liquid, and the diameter of the vein, instead 

 of being everywhere the same, decreases more or less in propor- 

 tion as we recede from the contracted section. 



If the causes which we have detailed were alone in action, the 



