" MOLECULAR COALESCENCE/' ETC. 235 



specimen this condition was more than reversed. The crys- 

 tals were at least ten times as numerous as the coalescence 

 formSj and were, on the average, more than twice the dia- 

 meter of the crystals in the warmer specimens. It will be 

 noticed that the crystalline form here remains perfect as long 

 as the crystal does not exceed a certain size. In the small 

 crystals the force of crystallization is strong enough to resist 

 the surrounding forces of disturbance. When the length of 

 the axes is extended, and the relations between the more 

 widely separated molecules become weaker, the line is 

 broken and disintegration of more or less completeness fol- 

 lows ; just as liquids in small quantities Avill form drops, 

 but only drops of a certain limit of size for each kind of 

 liquid. 



Experiments were also made with electricity, but were so 

 much complicated by electrolysis as to give no satisfactory 

 results. 



The next step was to institute comparisons with other salts. 

 Triple phosphate Avas first experimented on, the plug being 

 interposed between a solution of hydrodisodic phosphate 

 (phosphate of soda) and chloride of ammonium on the one 

 hand, and of sulphate of magnesiimi on the other. 



In the neighbourhood of the magnesic solution were found 

 small, not very perfect, crystals of the " house-top" form. In 

 the middle of the plug were large scattered masses, plainly 

 visible to the eye, often more than a line in diameter, and 

 consisting each of a central spherical body with many radi- 

 ating stalactitic arms, composed of aggregated and overlap- 

 ping prisms. The edges and angles were sharp on the mag- 

 nesic side, rounded, in conjunction with greatly diminished 

 size of the masses at the phosphatic end. Near the plios- 

 phatic end were subspherical, or crescentic, or unsymmetri- 

 cally sheaf-like tufts of fine radiating needles or raphides, 

 easily broken up by pressure. All these forms depolarized 

 light, the larger with brilliant play of colour, the smaller 

 with alterations of light and darkness. Phosphate of cal- 

 cium showed an equal power of resisting the influence of the 

 colloid. In Mr. Rainey's experiments it had been noticed 

 that the addition of phosphate to carbonate of calcium had 

 up to a point been attended with the production of larger 

 and more perfect spheres ; but the spheres were unstable, and 

 easily reverted to a crystalline condition, and when a certain 

 excess of phosphate was attained spheres could no longer be 

 produced. But it was certain that the phosphates entered 

 largely into the constitution of the hard bony structures of 

 animal bodies, and that the form in which they were therein 



