328 



GEORGE F. BECKER AND ARTHUR L. DAY 



offer, and indeed would seem to be without any foundation 

 whatsoever. 



We fail to see any reason for connecting the rise of the porcelain 

 disks with capillarity or with adsorption. These could only 

 obstruct the elevation, and must have been overcome by a linear 

 force attending the crystallization of the alum, as in our own 

 experiments. 



It is not expedient, however, to rely on reasoning alone in 

 matters of physics if experimentation is practicable, and we accord- 

 ingly made the effort to separate the forces to which Bruhns and 

 Mecklenburg appeal, through evaporation of solution of a colloid 

 (gum arabic) in which was immersed a block of glass replacing the 

 alum crystal between the two plates of glass (Table VII) . Evap- 

 oration to dryness caused no rise of the upper glass plate as it 



TABLE VII 



Block of Glass Replacing the Alum Crystal (Fig. i). Load (Glass Plate) = 

 24 Gm. Glass Block and Load Completely Immersed in 2 Per Cent Solu- 

 tion of Gum Arabic in Water. Room Temperature 



Refilled with 2 per cent gum arabic solution; all conditions unchanged 



58.8. 



68.8. 



76.1 . 



116. 9. 



37.2669 

 37.2670 

 37.2670 

 37-2653 



+0 . 006 

 +0.006 

 +0.006 

 +0 . 004 



Evaporated to dryness 



should have done were capillarity and adsorption the source of 

 energy. A saturated solution of alum added to the colloid 

 (Table VIII) starts crystal formation and growth at once, but at 

 a rate much slower than in the cases where no colloid was present. 

 This is in full accord with the experiments of Marc. 1 



In addition to confirming the results of Marc, Table VIII offers 

 independent and explicit experimental proof that the "linear force" 

 appears here also in spite of the action of the colloid in retarding 



1 See footnote, p. 326. 



