S. Taber — Growth of Crystals. 533 



Becker and Day state that "It was at once evident that it 

 amounted to many pounds per square inch, and as observations 

 multiplied, it became reasonably certain that it is actually of 

 the same order of magnitude as the ascertained resistance 

 which the crystals offered to crushing stresses."* 



Important as these conclusions are, the paper by Becker and 

 Day did not attract the immediate and general attention that it 

 deserved, possibly because it did not have as wide a distribu- 

 tion as it would have had if printed elsewhere than in the pro- 

 ceedings of a local society. And while it opened a wide field 

 for further research no one seems to have taken advantage of it. 



In 1913 two German investigators, Bruhns and Mecklen- 

 burg, published a paperf in which they claim to have repeated 

 the experiments of Becker and Day with negative results, and 

 they criticise the description of these experiments, stating that 

 it is not so accurate and full as one might expect in the case of 

 such a striking phenomenon.^: Their own paper is certainly 

 not open to this criticism, for they describe in the greatest 

 detail the manner in which their experiments were conducted. 



It is not necessary to repeat here all the details of their 

 experiments, but one detail is important as it evidently explains 

 why Bruhns and Mechlenburg obtained results differing from 

 those described by the two American scientists. In a crys- 

 tallizing dish containing a saturated solution of alum the Ger- 

 man investigators placed two crystals of alum of approximately 

 the same size and weight ; one of these ivas left uncovered, 

 while the other was covered with a glass plate on which was 

 placed a weight of one kilogram. § From time to time the 

 crystals were removed from the solution and after being care- 

 fully dried, were measured and weighed. The experiments 

 were repeated several times, the results obtained being tabulated. 

 An inspection of the tables shows that the height of the 

 unloaded crystals increased, while that of the loaded crystals 

 remained practically the same. Both increased in weight, 

 but the unloaded crystals gained nearly twice as much as the 

 loaded ones. 



Bruhns and Mecklenburg go further and state that the 

 weight resting on the covered crystal plays, as such, no 

 important role ; the essential thing being the circumstance that 

 the upper face of the crystal is protected from the addition 

 of further substance. | In proof of this statement they describe 

 another experiment in which four crystals of alum were placed 



*Ibid., pp. 286-287. 



f Bruhns, W. and Mecklenburg, Werner, Tiber die sogenannte " Kristall- 

 isationskraft," 6th Jahresbericht d. Niedersachsischen geologischen Vereins, 

 pp. 92-115, 1913. 



{Ibid, p. 96. glbid., p. 99. 



|| Ibid., p. 100. 



