COHESIDX OF FLUDIS* 



83 1 



tals are most easily amalgamated with mercury. It is proba- Application of 

 ble that such an amalgamation actually took place in some of 5^^,^^^^^^^^." 

 Uie experiments j and atiected their results, for the process of fluids, 

 ■imalgamation may often be observed to begin almost at the 

 instant of contact of silver with merciiryj and the want of per- 

 fect horizontality appears in slight degree to have affected them 

 all. A deviation of one-fiftieth of an inch would be sufficient to 

 have produced the difference between 446 grains and 528 ; and 

 it is not impossible that all the differences, as far down as bis- 

 muth, may have been accidental. But if we suppose the gold 

 only to have been perfectly wetted by the mercury, and all 

 the other numbers to be in due proportions, we may find the 

 appropriate angle for each substance by deducting from ISO", 

 twice the angle of which the sine is to the radius as the apparent 

 cohesion of each to 446" grains; that is, for gold .1, for silver 

 about QJi for tin .95, for lead .pOj for bismuth .85 for zinc. 

 .46, for copper .32, for antimony .29? for iron 26, and for 

 cobalt .02, neglecting the surrounding elevation, which has 

 less effect in proportion as the surface employed is larger. Gel- 

 lert found the depression of melted lead in a tube of glass 

 multiplied by the bore equal to about .0054. 



It would perhaps be possible to pursue these principles sol 

 far as to determine in many cases the circumstances under 

 which a drop of any fluid would detach itself from a given 

 surface. But it is sufficient to infer, from the law of the su- 

 perficial cohesion of fluids, that the linear dimensions of simi- 

 lar drops depending from a horizontal surface must vary pre- 

 cisely in the same ratio as the heights of ascent of the resjiec* 

 tivc fluids against a vertical surface, or as the square root of 

 the heights of ascent in a given tube; hence the magnitudes 

 of similar drops of different fluids must vary as the cubes of 

 the square roots of the heights of ascent in a tube. I have 

 measured the heights of ascent of water and of diluted sjiint 

 of wine in the same tube, and I found tl>cm nearly as ]0() to 

 64; a drop of water falling from a large sphere of glass 

 ueighed 1.8 grains, a drop of the spirit of wine about .85, 

 instead of .82, which is nearly the weight that would be in- 

 ferred from the consideration of the heights of ascent, com- 

 bined with that of the specific gravities. We may fbnn a 

 conjecture respecting the probable magnitude of a dro]) by 

 M 2 iiiquinnir 



