THE LINEAR FORCE OF GROWING CRYSTALS 



3 2 5 



have grown alone until it shared the load, after which both crystals 

 would have grown at rates approximately in inverse relation to 

 their individual shares. 



The effect of distributing a load over three crystals is shown by 

 a simple case (Table VI). 



TABLE VI 

 Exposure 3 Days. Temperature about 20 . Load 200 Gm. 



Nor is it necessary that the measurements given in this table 

 should stand alone in support of so important a conclusion. 

 Bruhns and Mecklenburg succeeded in raising disks of porcelain 

 loaded with weighted beaker-glasses, by the help of the crystalliza- 

 tion of chrome alum, to elevations of a millimeter and more under 

 certain conditions. These conditions were that the solution in 

 contact with the disks and their load should be allowed to evaporate 

 to dryness, the maximum elevations resulting when fresh portions 

 of saturated solution were added and evaporated successively. 

 These observations were not measured in detail, but are sufficiently 

 well described in the following paragraphs (Bruhns and Mecklen- 

 burg, op. cit. pp., 107 and 108): 



"Greater or less loading of the little beaker-glasses made no difference in 

 the crystal development. All the six beakers — and this is the important point 

 — no longer rested upon the porcelain disk but rather upon chrome alum 

 crystals. After breaking the glasses loose, it was possible to establish beyond 

 doubt that the crystals which supported the loaded beaker-glasses were at 

 least 1 mm. thick, in many places even thicker, and the glass was no longer 

 anywhere in contact with the porcelain supports" [p. 107]. 



"After a fragment of the crystallizing dish was broken away, in order to 

 obtain a vertical section through the system, it could also be plainly seen that 

 the porcelain disks no longer touched the bottom of the dish at any point, but 

 were separated from it by a crystal layer the measured thickness of which was 



