" MOLECULAR COALESCENCE^^ ETC. 233 



late of calcium, when they had once ceased to be crystalline, 

 assume different coalescence forms ? This might be due to 

 the fact that, their crystalline form being different, their mole- 

 cules still tended to repulsions or attractions among themselves 

 in certain directions, and so modified the sphere-forming 

 force, or their different degrees of hydration or of solubility 

 might have influence. The lines of weakening of the cohe- 

 sion of crystals must evidently be carefully noted. 



Before complicating the evidence by using solutions of other 

 salts than those mentioned, it became desirable to determine 

 whether the action of the colloid upon the oxalate and car- 

 bonate of calcium could be modified by the influence of the 

 various physical forces. The curious viscosity of magnetism 

 — first, I believe, demonstrated by Faraday, and clearly de- 

 scribed by Professor Tyndall in his work on Heat — here sug- 

 gested itself as not unlikely to intensify the viscosity of the 

 colloid. 



Common horse-shoe magnets of moderate power were at first 

 used. In some experiments, the plugged tubes being arranged 

 as in the first experiment, the magnets Avere so placed that the 

 line of greatest deposit would run between their poles, in 

 other cases, so that the length of the plug would be parallel 

 to the line joining the polos. In other experiments little jars 

 were partly filled with gelatin imbued with chloride of cal- 

 cium, the poles thrust into the gelatin while warm, and the 

 jars, on cooling, filled up with solution of oxalate of ammonia. 

 The general result was that there was an extraordinary increase 

 in the size of all the forms, crystalline and non-crystalline^ 

 where the plug or gelatin was subjected to the action of mag- 

 netism, but that there was no production of new forms or 

 greater tendency to sphericity (PL XYI, fig. 7). 



Similar experiments were made with an electro-magnet 

 capable, with the means at hand, of sustaining a weight of 

 thirty pounds. Some of the crystals in several cases appeared 

 to have their axes slightly twisted ; it would be very interest- 

 ing to know if this and the direction of the axis generally bore 

 any relation to the direction of the interpolar line, a point to 

 which I intend to recur at some future period. 



At the time of making these last experiments I Avas under 

 the impression that the so-called viscosity of magnetism 

 was a condition of resistance by inertia ; but Mr. Charles 

 Brooke has made me aware that he has proved this viscosity to 

 depend upon the existence of strong spiral currents in the 

 magnetic arc. At about the same time I had come to doubt 

 whether the sphere-forming influence of colloids was a simple 

 act of passive resistance. The perpetual change characteristic 



